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llvm-mirror/lib/Target/X86/X86FrameLowering.cpp
Martin Storsjo 37c24a1860 [X86] Handle EAX being live when calling chkstk for x86_64 
EAX can turn out to be alive here, when shrink wrapping is done
(which is allowed when using dwarf exceptions, contrary to the
normal case with WinCFI).

This fixes PR36487.

Differential Revision: https://reviews.llvm.org/D43968

llvm-svn: 326764
2018-03-06 06:00:13 +00:00

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//===-- X86FrameLowering.cpp - X86 Frame Information ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the X86 implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "X86FrameLowering.h"
#include "X86InstrBuilder.h"
#include "X86InstrInfo.h"
#include "X86MachineFunctionInfo.h"
#include "X86Subtarget.h"
#include "X86TargetMachine.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetOptions.h"
#include <cstdlib>
using namespace llvm;
X86FrameLowering::X86FrameLowering(const X86Subtarget &STI,
unsigned StackAlignOverride)
: TargetFrameLowering(StackGrowsDown, StackAlignOverride,
STI.is64Bit() ? -8 : -4),
STI(STI), TII(*STI.getInstrInfo()), TRI(STI.getRegisterInfo()) {
// Cache a bunch of frame-related predicates for this subtarget.
SlotSize = TRI->getSlotSize();
Is64Bit = STI.is64Bit();
IsLP64 = STI.isTarget64BitLP64();
// standard x86_64 and NaCl use 64-bit frame/stack pointers, x32 - 32-bit.
Uses64BitFramePtr = STI.isTarget64BitLP64() || STI.isTargetNaCl64();
StackPtr = TRI->getStackRegister();
}
bool X86FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
return !MF.getFrameInfo().hasVarSizedObjects() &&
!MF.getInfo<X86MachineFunctionInfo>()->getHasPushSequences();
}
/// canSimplifyCallFramePseudos - If there is a reserved call frame, the
/// call frame pseudos can be simplified. Having a FP, as in the default
/// implementation, is not sufficient here since we can't always use it.
/// Use a more nuanced condition.
bool
X86FrameLowering::canSimplifyCallFramePseudos(const MachineFunction &MF) const {
return hasReservedCallFrame(MF) ||
(hasFP(MF) && !TRI->needsStackRealignment(MF)) ||
TRI->hasBasePointer(MF);
}
// needsFrameIndexResolution - Do we need to perform FI resolution for
// this function. Normally, this is required only when the function
// has any stack objects. However, FI resolution actually has another job,
// not apparent from the title - it resolves callframesetup/destroy
// that were not simplified earlier.
// So, this is required for x86 functions that have push sequences even
// when there are no stack objects.
bool
X86FrameLowering::needsFrameIndexResolution(const MachineFunction &MF) const {
return MF.getFrameInfo().hasStackObjects() ||
MF.getInfo<X86MachineFunctionInfo>()->getHasPushSequences();
}
/// hasFP - Return true if the specified function should have a dedicated frame
/// pointer register. This is true if the function has variable sized allocas
/// or if frame pointer elimination is disabled.
bool X86FrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
return (MF.getTarget().Options.DisableFramePointerElim(MF) ||
TRI->needsStackRealignment(MF) ||
MFI.hasVarSizedObjects() ||
MFI.isFrameAddressTaken() || MFI.hasOpaqueSPAdjustment() ||
MF.getInfo<X86MachineFunctionInfo>()->getForceFramePointer() ||
MF.callsUnwindInit() || MF.hasEHFunclets() || MF.callsEHReturn() ||
MFI.hasStackMap() || MFI.hasPatchPoint() ||
MFI.hasCopyImplyingStackAdjustment());
}
static unsigned getSUBriOpcode(unsigned IsLP64, int64_t Imm) {
if (IsLP64) {
if (isInt<8>(Imm))
return X86::SUB64ri8;
return X86::SUB64ri32;
} else {
if (isInt<8>(Imm))
return X86::SUB32ri8;
return X86::SUB32ri;
}
}
static unsigned getADDriOpcode(unsigned IsLP64, int64_t Imm) {
if (IsLP64) {
if (isInt<8>(Imm))
return X86::ADD64ri8;
return X86::ADD64ri32;
} else {
if (isInt<8>(Imm))
return X86::ADD32ri8;
return X86::ADD32ri;
}
}
static unsigned getSUBrrOpcode(unsigned isLP64) {
return isLP64 ? X86::SUB64rr : X86::SUB32rr;
}
static unsigned getADDrrOpcode(unsigned isLP64) {
return isLP64 ? X86::ADD64rr : X86::ADD32rr;
}
static unsigned getANDriOpcode(bool IsLP64, int64_t Imm) {
if (IsLP64) {
if (isInt<8>(Imm))
return X86::AND64ri8;
return X86::AND64ri32;
}
if (isInt<8>(Imm))
return X86::AND32ri8;
return X86::AND32ri;
}
static unsigned getLEArOpcode(unsigned IsLP64) {
return IsLP64 ? X86::LEA64r : X86::LEA32r;
}
/// findDeadCallerSavedReg - Return a caller-saved register that isn't live
/// when it reaches the "return" instruction. We can then pop a stack object
/// to this register without worry about clobbering it.
static unsigned findDeadCallerSavedReg(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
const X86RegisterInfo *TRI,
bool Is64Bit) {
const MachineFunction *MF = MBB.getParent();
if (MF->callsEHReturn())
return 0;
const TargetRegisterClass &AvailableRegs = *TRI->getGPRsForTailCall(*MF);
if (MBBI == MBB.end())
return 0;
switch (MBBI->getOpcode()) {
default: return 0;
case TargetOpcode::PATCHABLE_RET:
case X86::RET:
case X86::RETL:
case X86::RETQ:
case X86::RETIL:
case X86::RETIQ:
case X86::TCRETURNdi:
case X86::TCRETURNri:
case X86::TCRETURNmi:
case X86::TCRETURNdi64:
case X86::TCRETURNri64:
case X86::TCRETURNmi64:
case X86::EH_RETURN:
case X86::EH_RETURN64: {
SmallSet<uint16_t, 8> Uses;
for (unsigned i = 0, e = MBBI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MBBI->getOperand(i);
if (!MO.isReg() || MO.isDef())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
Uses.insert(*AI);
}
for (auto CS : AvailableRegs)
if (!Uses.count(CS) && CS != X86::RIP)
return CS;
}
}
return 0;
}
static bool isEAXLiveIn(MachineBasicBlock &MBB) {
for (MachineBasicBlock::RegisterMaskPair RegMask : MBB.liveins()) {
unsigned Reg = RegMask.PhysReg;
if (Reg == X86::RAX || Reg == X86::EAX || Reg == X86::AX ||
Reg == X86::AH || Reg == X86::AL)
return true;
}
return false;
}
/// Check if the flags need to be preserved before the terminators.
/// This would be the case, if the eflags is live-in of the region
/// composed by the terminators or live-out of that region, without
/// being defined by a terminator.
static bool
flagsNeedToBePreservedBeforeTheTerminators(const MachineBasicBlock &MBB) {
for (const MachineInstr &MI : MBB.terminators()) {
bool BreakNext = false;
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (Reg != X86::EFLAGS)
continue;
// This terminator needs an eflags that is not defined
// by a previous another terminator:
// EFLAGS is live-in of the region composed by the terminators.
if (!MO.isDef())
return true;
// This terminator defines the eflags, i.e., we don't need to preserve it.
// However, we still need to check this specific terminator does not
// read a live-in value.
BreakNext = true;
}
// We found a definition of the eflags, no need to preserve them.
if (BreakNext)
return false;
}
// None of the terminators use or define the eflags.
// Check if they are live-out, that would imply we need to preserve them.
for (const MachineBasicBlock *Succ : MBB.successors())
if (Succ->isLiveIn(X86::EFLAGS))
return true;
return false;
}
/// emitSPUpdate - Emit a series of instructions to increment / decrement the
/// stack pointer by a constant value.
void X86FrameLowering::emitSPUpdate(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
const DebugLoc &DL,
int64_t NumBytes, bool InEpilogue) const {
bool isSub = NumBytes < 0;
uint64_t Offset = isSub ? -NumBytes : NumBytes;
MachineInstr::MIFlag Flag =
isSub ? MachineInstr::FrameSetup : MachineInstr::FrameDestroy;
uint64_t Chunk = (1LL << 31) - 1;
if (Offset > Chunk) {
// Rather than emit a long series of instructions for large offsets,
// load the offset into a register and do one sub/add
unsigned Reg = 0;
unsigned Rax = (unsigned)(Is64Bit ? X86::RAX : X86::EAX);
if (isSub && !isEAXLiveIn(MBB))
Reg = Rax;
else
Reg = findDeadCallerSavedReg(MBB, MBBI, TRI, Is64Bit);
unsigned MovRIOpc = Is64Bit ? X86::MOV64ri : X86::MOV32ri;
unsigned AddSubRROpc =
isSub ? getSUBrrOpcode(Is64Bit) : getADDrrOpcode(Is64Bit);
if (Reg) {
BuildMI(MBB, MBBI, DL, TII.get(MovRIOpc), Reg)
.addImm(Offset)
.setMIFlag(Flag);
MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(AddSubRROpc), StackPtr)
.addReg(StackPtr)
.addReg(Reg);
MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
return;
} else if (Offset > 8 * Chunk) {
// If we would need more than 8 add or sub instructions (a >16GB stack
// frame), it's worth spilling RAX to materialize this immediate.
// pushq %rax
// movabsq +-$Offset+-SlotSize, %rax
// addq %rsp, %rax
// xchg %rax, (%rsp)
// movq (%rsp), %rsp
assert(Is64Bit && "can't have 32-bit 16GB stack frame");
BuildMI(MBB, MBBI, DL, TII.get(X86::PUSH64r))
.addReg(Rax, RegState::Kill)
.setMIFlag(Flag);
// Subtract is not commutative, so negate the offset and always use add.
// Subtract 8 less and add 8 more to account for the PUSH we just did.
if (isSub)
Offset = -(Offset - SlotSize);
else
Offset = Offset + SlotSize;
BuildMI(MBB, MBBI, DL, TII.get(MovRIOpc), Rax)
.addImm(Offset)
.setMIFlag(Flag);
MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(X86::ADD64rr), Rax)
.addReg(Rax)
.addReg(StackPtr);
MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
// Exchange the new SP in RAX with the top of the stack.
addRegOffset(
BuildMI(MBB, MBBI, DL, TII.get(X86::XCHG64rm), Rax).addReg(Rax),
StackPtr, false, 0);
// Load new SP from the top of the stack into RSP.
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64rm), StackPtr),
StackPtr, false, 0);
return;
}
}
while (Offset) {
uint64_t ThisVal = std::min(Offset, Chunk);
if (ThisVal == SlotSize) {
// Use push / pop for slot sized adjustments as a size optimization. We
// need to find a dead register when using pop.
unsigned Reg = isSub
? (unsigned)(Is64Bit ? X86::RAX : X86::EAX)
: findDeadCallerSavedReg(MBB, MBBI, TRI, Is64Bit);
if (Reg) {
unsigned Opc = isSub
? (Is64Bit ? X86::PUSH64r : X86::PUSH32r)
: (Is64Bit ? X86::POP64r : X86::POP32r);
BuildMI(MBB, MBBI, DL, TII.get(Opc))
.addReg(Reg, getDefRegState(!isSub) | getUndefRegState(isSub))
.setMIFlag(Flag);
Offset -= ThisVal;
continue;
}
}
BuildStackAdjustment(MBB, MBBI, DL, isSub ? -ThisVal : ThisVal, InEpilogue)
.setMIFlag(Flag);
Offset -= ThisVal;
}
}
MachineInstrBuilder X86FrameLowering::BuildStackAdjustment(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
const DebugLoc &DL, int64_t Offset, bool InEpilogue) const {
assert(Offset != 0 && "zero offset stack adjustment requested");
// On Atom, using LEA to adjust SP is preferred, but using it in the epilogue
// is tricky.
bool UseLEA;
if (!InEpilogue) {
// Check if inserting the prologue at the beginning
// of MBB would require to use LEA operations.
// We need to use LEA operations if EFLAGS is live in, because
// it means an instruction will read it before it gets defined.
UseLEA = STI.useLeaForSP() || MBB.isLiveIn(X86::EFLAGS);
} else {
// If we can use LEA for SP but we shouldn't, check that none
// of the terminators uses the eflags. Otherwise we will insert
// a ADD that will redefine the eflags and break the condition.
// Alternatively, we could move the ADD, but this may not be possible
// and is an optimization anyway.
UseLEA = canUseLEAForSPInEpilogue(*MBB.getParent());
if (UseLEA && !STI.useLeaForSP())
UseLEA = flagsNeedToBePreservedBeforeTheTerminators(MBB);
// If that assert breaks, that means we do not do the right thing
// in canUseAsEpilogue.
assert((UseLEA || !flagsNeedToBePreservedBeforeTheTerminators(MBB)) &&
"We shouldn't have allowed this insertion point");
}
MachineInstrBuilder MI;
if (UseLEA) {
MI = addRegOffset(BuildMI(MBB, MBBI, DL,
TII.get(getLEArOpcode(Uses64BitFramePtr)),
StackPtr),
StackPtr, false, Offset);
} else {
bool IsSub = Offset < 0;
uint64_t AbsOffset = IsSub ? -Offset : Offset;
unsigned Opc = IsSub ? getSUBriOpcode(Uses64BitFramePtr, AbsOffset)
: getADDriOpcode(Uses64BitFramePtr, AbsOffset);
MI = BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr)
.addReg(StackPtr)
.addImm(AbsOffset);
MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
}
return MI;
}
int X86FrameLowering::mergeSPUpdates(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
bool doMergeWithPrevious) const {
if ((doMergeWithPrevious && MBBI == MBB.begin()) ||
(!doMergeWithPrevious && MBBI == MBB.end()))
return 0;
MachineBasicBlock::iterator PI = doMergeWithPrevious ? std::prev(MBBI) : MBBI;
MachineBasicBlock::iterator NI = doMergeWithPrevious ? nullptr
: std::next(MBBI);
PI = skipDebugInstructionsBackward(PI, MBB.begin());
if (NI != nullptr)
NI = skipDebugInstructionsForward(NI, MBB.end());
unsigned Opc = PI->getOpcode();
int Offset = 0;
if (!doMergeWithPrevious && NI != MBB.end() &&
NI->getOpcode() == TargetOpcode::CFI_INSTRUCTION) {
// Don't merge with the next instruction if it has CFI.
return Offset;
}
if ((Opc == X86::ADD64ri32 || Opc == X86::ADD64ri8 ||
Opc == X86::ADD32ri || Opc == X86::ADD32ri8) &&
PI->getOperand(0).getReg() == StackPtr){
assert(PI->getOperand(1).getReg() == StackPtr);
Offset += PI->getOperand(2).getImm();
MBB.erase(PI);
if (!doMergeWithPrevious) MBBI = NI;
} else if ((Opc == X86::LEA32r || Opc == X86::LEA64_32r) &&
PI->getOperand(0).getReg() == StackPtr &&
PI->getOperand(1).getReg() == StackPtr &&
PI->getOperand(2).getImm() == 1 &&
PI->getOperand(3).getReg() == X86::NoRegister &&
PI->getOperand(5).getReg() == X86::NoRegister) {
// For LEAs we have: def = lea SP, FI, noreg, Offset, noreg.
Offset += PI->getOperand(4).getImm();
MBB.erase(PI);
if (!doMergeWithPrevious) MBBI = NI;
} else if ((Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
Opc == X86::SUB32ri || Opc == X86::SUB32ri8) &&
PI->getOperand(0).getReg() == StackPtr) {
assert(PI->getOperand(1).getReg() == StackPtr);
Offset -= PI->getOperand(2).getImm();
MBB.erase(PI);
if (!doMergeWithPrevious) MBBI = NI;
}
return Offset;
}
void X86FrameLowering::BuildCFI(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL,
const MCCFIInstruction &CFIInst) const {
MachineFunction &MF = *MBB.getParent();
unsigned CFIIndex = MF.addFrameInst(CFIInst);
BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
void X86FrameLowering::emitCalleeSavedFrameMoves(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
const DebugLoc &DL) const {
MachineFunction &MF = *MBB.getParent();
MachineFrameInfo &MFI = MF.getFrameInfo();
MachineModuleInfo &MMI = MF.getMMI();
const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
// Add callee saved registers to move list.
const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
if (CSI.empty()) return;
// Calculate offsets.
for (std::vector<CalleeSavedInfo>::const_iterator
I = CSI.begin(), E = CSI.end(); I != E; ++I) {
int64_t Offset = MFI.getObjectOffset(I->getFrameIdx());
unsigned Reg = I->getReg();
unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
BuildCFI(MBB, MBBI, DL,
MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
}
}
void X86FrameLowering::emitStackProbe(MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL, bool InProlog) const {
const X86Subtarget &STI = MF.getSubtarget<X86Subtarget>();
if (STI.isTargetWindowsCoreCLR()) {
if (InProlog) {
emitStackProbeInlineStub(MF, MBB, MBBI, DL, true);
} else {
emitStackProbeInline(MF, MBB, MBBI, DL, false);
}
} else {
emitStackProbeCall(MF, MBB, MBBI, DL, InProlog);
}
}
void X86FrameLowering::inlineStackProbe(MachineFunction &MF,
MachineBasicBlock &PrologMBB) const {
const StringRef ChkStkStubSymbol = "__chkstk_stub";
MachineInstr *ChkStkStub = nullptr;
for (MachineInstr &MI : PrologMBB) {
if (MI.isCall() && MI.getOperand(0).isSymbol() &&
ChkStkStubSymbol == MI.getOperand(0).getSymbolName()) {
ChkStkStub = &MI;
break;
}
}
if (ChkStkStub != nullptr) {
assert(!ChkStkStub->isBundled() &&
"Not expecting bundled instructions here");
MachineBasicBlock::iterator MBBI = std::next(ChkStkStub->getIterator());
assert(std::prev(MBBI) == ChkStkStub &&
"MBBI expected after __chkstk_stub.");
DebugLoc DL = PrologMBB.findDebugLoc(MBBI);
emitStackProbeInline(MF, PrologMBB, MBBI, DL, true);
ChkStkStub->eraseFromParent();
}
}
void X86FrameLowering::emitStackProbeInline(MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL,
bool InProlog) const {
const X86Subtarget &STI = MF.getSubtarget<X86Subtarget>();
assert(STI.is64Bit() && "different expansion needed for 32 bit");
assert(STI.isTargetWindowsCoreCLR() && "custom expansion expects CoreCLR");
const TargetInstrInfo &TII = *STI.getInstrInfo();
const BasicBlock *LLVM_BB = MBB.getBasicBlock();
// RAX contains the number of bytes of desired stack adjustment.
// The handling here assumes this value has already been updated so as to
// maintain stack alignment.
//
// We need to exit with RSP modified by this amount and execute suitable
// page touches to notify the OS that we're growing the stack responsibly.
// All stack probing must be done without modifying RSP.
//
// MBB:
// SizeReg = RAX;
// ZeroReg = 0
// CopyReg = RSP
// Flags, TestReg = CopyReg - SizeReg
// FinalReg = !Flags.Ovf ? TestReg : ZeroReg
// LimitReg = gs magic thread env access
// if FinalReg >= LimitReg goto ContinueMBB
// RoundBB:
// RoundReg = page address of FinalReg
// LoopMBB:
// LoopReg = PHI(LimitReg,ProbeReg)
// ProbeReg = LoopReg - PageSize
// [ProbeReg] = 0
// if (ProbeReg > RoundReg) goto LoopMBB
// ContinueMBB:
// RSP = RSP - RAX
// [rest of original MBB]
// Set up the new basic blocks
MachineBasicBlock *RoundMBB = MF.CreateMachineBasicBlock(LLVM_BB);
MachineBasicBlock *LoopMBB = MF.CreateMachineBasicBlock(LLVM_BB);
MachineBasicBlock *ContinueMBB = MF.CreateMachineBasicBlock(LLVM_BB);
MachineFunction::iterator MBBIter = std::next(MBB.getIterator());
MF.insert(MBBIter, RoundMBB);
MF.insert(MBBIter, LoopMBB);
MF.insert(MBBIter, ContinueMBB);
// Split MBB and move the tail portion down to ContinueMBB.
MachineBasicBlock::iterator BeforeMBBI = std::prev(MBBI);
ContinueMBB->splice(ContinueMBB->begin(), &MBB, MBBI, MBB.end());
ContinueMBB->transferSuccessorsAndUpdatePHIs(&MBB);
// Some useful constants
const int64_t ThreadEnvironmentStackLimit = 0x10;
const int64_t PageSize = 0x1000;
const int64_t PageMask = ~(PageSize - 1);
// Registers we need. For the normal case we use virtual
// registers. For the prolog expansion we use RAX, RCX and RDX.
MachineRegisterInfo &MRI = MF.getRegInfo();
const TargetRegisterClass *RegClass = &X86::GR64RegClass;
const unsigned SizeReg = InProlog ? (unsigned)X86::RAX
: MRI.createVirtualRegister(RegClass),
ZeroReg = InProlog ? (unsigned)X86::RCX
: MRI.createVirtualRegister(RegClass),
CopyReg = InProlog ? (unsigned)X86::RDX
: MRI.createVirtualRegister(RegClass),
TestReg = InProlog ? (unsigned)X86::RDX
: MRI.createVirtualRegister(RegClass),
FinalReg = InProlog ? (unsigned)X86::RDX
: MRI.createVirtualRegister(RegClass),
RoundedReg = InProlog ? (unsigned)X86::RDX
: MRI.createVirtualRegister(RegClass),
LimitReg = InProlog ? (unsigned)X86::RCX
: MRI.createVirtualRegister(RegClass),
JoinReg = InProlog ? (unsigned)X86::RCX
: MRI.createVirtualRegister(RegClass),
ProbeReg = InProlog ? (unsigned)X86::RCX
: MRI.createVirtualRegister(RegClass);
// SP-relative offsets where we can save RCX and RDX.
int64_t RCXShadowSlot = 0;
int64_t RDXShadowSlot = 0;
// If inlining in the prolog, save RCX and RDX.
// Future optimization: don't save or restore if not live in.
if (InProlog) {
// Compute the offsets. We need to account for things already
// pushed onto the stack at this point: return address, frame
// pointer (if used), and callee saves.
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
const int64_t CalleeSaveSize = X86FI->getCalleeSavedFrameSize();
const bool HasFP = hasFP(MF);
RCXShadowSlot = 8 + CalleeSaveSize + (HasFP ? 8 : 0);
RDXShadowSlot = RCXShadowSlot + 8;
// Emit the saves.
addRegOffset(BuildMI(&MBB, DL, TII.get(X86::MOV64mr)), X86::RSP, false,
RCXShadowSlot)
.addReg(X86::RCX);
addRegOffset(BuildMI(&MBB, DL, TII.get(X86::MOV64mr)), X86::RSP, false,
RDXShadowSlot)
.addReg(X86::RDX);
} else {
// Not in the prolog. Copy RAX to a virtual reg.
BuildMI(&MBB, DL, TII.get(X86::MOV64rr), SizeReg).addReg(X86::RAX);
}
// Add code to MBB to check for overflow and set the new target stack pointer
// to zero if so.
BuildMI(&MBB, DL, TII.get(X86::XOR64rr), ZeroReg)
.addReg(ZeroReg, RegState::Undef)
.addReg(ZeroReg, RegState::Undef);
BuildMI(&MBB, DL, TII.get(X86::MOV64rr), CopyReg).addReg(X86::RSP);
BuildMI(&MBB, DL, TII.get(X86::SUB64rr), TestReg)
.addReg(CopyReg)
.addReg(SizeReg);
BuildMI(&MBB, DL, TII.get(X86::CMOVB64rr), FinalReg)
.addReg(TestReg)
.addReg(ZeroReg);
// FinalReg now holds final stack pointer value, or zero if
// allocation would overflow. Compare against the current stack
// limit from the thread environment block. Note this limit is the
// lowest touched page on the stack, not the point at which the OS
// will cause an overflow exception, so this is just an optimization
// to avoid unnecessarily touching pages that are below the current
// SP but already committed to the stack by the OS.
BuildMI(&MBB, DL, TII.get(X86::MOV64rm), LimitReg)
.addReg(0)
.addImm(1)
.addReg(0)
.addImm(ThreadEnvironmentStackLimit)
.addReg(X86::GS);
BuildMI(&MBB, DL, TII.get(X86::CMP64rr)).addReg(FinalReg).addReg(LimitReg);
// Jump if the desired stack pointer is at or above the stack limit.
BuildMI(&MBB, DL, TII.get(X86::JAE_1)).addMBB(ContinueMBB);
// Add code to roundMBB to round the final stack pointer to a page boundary.
BuildMI(RoundMBB, DL, TII.get(X86::AND64ri32), RoundedReg)
.addReg(FinalReg)
.addImm(PageMask);
BuildMI(RoundMBB, DL, TII.get(X86::JMP_1)).addMBB(LoopMBB);
// LimitReg now holds the current stack limit, RoundedReg page-rounded
// final RSP value. Add code to loopMBB to decrement LimitReg page-by-page
// and probe until we reach RoundedReg.
if (!InProlog) {
BuildMI(LoopMBB, DL, TII.get(X86::PHI), JoinReg)
.addReg(LimitReg)
.addMBB(RoundMBB)
.addReg(ProbeReg)
.addMBB(LoopMBB);
}
addRegOffset(BuildMI(LoopMBB, DL, TII.get(X86::LEA64r), ProbeReg), JoinReg,
false, -PageSize);
// Probe by storing a byte onto the stack.
BuildMI(LoopMBB, DL, TII.get(X86::MOV8mi))
.addReg(ProbeReg)
.addImm(1)
.addReg(0)
.addImm(0)
.addReg(0)
.addImm(0);
BuildMI(LoopMBB, DL, TII.get(X86::CMP64rr))
.addReg(RoundedReg)
.addReg(ProbeReg);
BuildMI(LoopMBB, DL, TII.get(X86::JNE_1)).addMBB(LoopMBB);
MachineBasicBlock::iterator ContinueMBBI = ContinueMBB->getFirstNonPHI();
// If in prolog, restore RDX and RCX.
if (InProlog) {
addRegOffset(BuildMI(*ContinueMBB, ContinueMBBI, DL, TII.get(X86::MOV64rm),
X86::RCX),
X86::RSP, false, RCXShadowSlot);
addRegOffset(BuildMI(*ContinueMBB, ContinueMBBI, DL, TII.get(X86::MOV64rm),
X86::RDX),
X86::RSP, false, RDXShadowSlot);
}
// Now that the probing is done, add code to continueMBB to update
// the stack pointer for real.
BuildMI(*ContinueMBB, ContinueMBBI, DL, TII.get(X86::SUB64rr), X86::RSP)
.addReg(X86::RSP)
.addReg(SizeReg);
// Add the control flow edges we need.
MBB.addSuccessor(ContinueMBB);
MBB.addSuccessor(RoundMBB);
RoundMBB->addSuccessor(LoopMBB);
LoopMBB->addSuccessor(ContinueMBB);
LoopMBB->addSuccessor(LoopMBB);
// Mark all the instructions added to the prolog as frame setup.
if (InProlog) {
for (++BeforeMBBI; BeforeMBBI != MBB.end(); ++BeforeMBBI) {
BeforeMBBI->setFlag(MachineInstr::FrameSetup);
}
for (MachineInstr &MI : *RoundMBB) {
MI.setFlag(MachineInstr::FrameSetup);
}
for (MachineInstr &MI : *LoopMBB) {
MI.setFlag(MachineInstr::FrameSetup);
}
for (MachineBasicBlock::iterator CMBBI = ContinueMBB->begin();
CMBBI != ContinueMBBI; ++CMBBI) {
CMBBI->setFlag(MachineInstr::FrameSetup);
}
}
// Possible TODO: physreg liveness for InProlog case.
}
void X86FrameLowering::emitStackProbeCall(MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL,
bool InProlog) const {
bool IsLargeCodeModel = MF.getTarget().getCodeModel() == CodeModel::Large;
// FIXME: Add retpoline support and remove this.
if (Is64Bit && IsLargeCodeModel && STI.useRetpoline())
report_fatal_error("Emitting stack probe calls on 64-bit with the large "
"code model and retpoline not yet implemented.");
unsigned CallOp;
if (Is64Bit)
CallOp = IsLargeCodeModel ? X86::CALL64r : X86::CALL64pcrel32;
else
CallOp = X86::CALLpcrel32;
StringRef Symbol = STI.getTargetLowering()->getStackProbeSymbolName(MF);
MachineInstrBuilder CI;
MachineBasicBlock::iterator ExpansionMBBI = std::prev(MBBI);
// All current stack probes take AX and SP as input, clobber flags, and
// preserve all registers. x86_64 probes leave RSP unmodified.
if (Is64Bit && MF.getTarget().getCodeModel() == CodeModel::Large) {
// For the large code model, we have to call through a register. Use R11,
// as it is scratch in all supported calling conventions.
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64ri), X86::R11)
.addExternalSymbol(MF.createExternalSymbolName(Symbol));
CI = BuildMI(MBB, MBBI, DL, TII.get(CallOp)).addReg(X86::R11);
} else {
CI = BuildMI(MBB, MBBI, DL, TII.get(CallOp))
.addExternalSymbol(MF.createExternalSymbolName(Symbol));
}
unsigned AX = Is64Bit ? X86::RAX : X86::EAX;
unsigned SP = Is64Bit ? X86::RSP : X86::ESP;
CI.addReg(AX, RegState::Implicit)
.addReg(SP, RegState::Implicit)
.addReg(AX, RegState::Define | RegState::Implicit)
.addReg(SP, RegState::Define | RegState::Implicit)
.addReg(X86::EFLAGS, RegState::Define | RegState::Implicit);
if (STI.isTargetWin64() || !STI.isOSWindows()) {
// MSVC x32's _chkstk and cygwin/mingw's _alloca adjust %esp themselves.
// MSVC x64's __chkstk and cygwin/mingw's ___chkstk_ms do not adjust %rsp
// themselves. They also does not clobber %rax so we can reuse it when
// adjusting %rsp.
// All other platforms do not specify a particular ABI for the stack probe
// function, so we arbitrarily define it to not adjust %esp/%rsp itself.
BuildMI(MBB, MBBI, DL, TII.get(getSUBrrOpcode(Is64Bit)), SP)
.addReg(SP)
.addReg(AX);
}
if (InProlog) {
// Apply the frame setup flag to all inserted instrs.
for (++ExpansionMBBI; ExpansionMBBI != MBBI; ++ExpansionMBBI)
ExpansionMBBI->setFlag(MachineInstr::FrameSetup);
}
}
void X86FrameLowering::emitStackProbeInlineStub(
MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI, const DebugLoc &DL, bool InProlog) const {
assert(InProlog && "ChkStkStub called outside prolog!");
BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
.addExternalSymbol("__chkstk_stub");
}
static unsigned calculateSetFPREG(uint64_t SPAdjust) {
// Win64 ABI has a less restrictive limitation of 240; 128 works equally well
// and might require smaller successive adjustments.
const uint64_t Win64MaxSEHOffset = 128;
uint64_t SEHFrameOffset = std::min(SPAdjust, Win64MaxSEHOffset);
// Win64 ABI requires 16-byte alignment for the UWOP_SET_FPREG opcode.
return SEHFrameOffset & -16;
}
// If we're forcing a stack realignment we can't rely on just the frame
// info, we need to know the ABI stack alignment as well in case we
// have a call out. Otherwise just make sure we have some alignment - we'll
// go with the minimum SlotSize.
uint64_t X86FrameLowering::calculateMaxStackAlign(const MachineFunction &MF) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
uint64_t MaxAlign = MFI.getMaxAlignment(); // Desired stack alignment.
unsigned StackAlign = getStackAlignment();
if (MF.getFunction().hasFnAttribute("stackrealign")) {
if (MFI.hasCalls())
MaxAlign = (StackAlign > MaxAlign) ? StackAlign : MaxAlign;
else if (MaxAlign < SlotSize)
MaxAlign = SlotSize;
}
return MaxAlign;
}
void X86FrameLowering::BuildStackAlignAND(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL, unsigned Reg,
uint64_t MaxAlign) const {
uint64_t Val = -MaxAlign;
unsigned AndOp = getANDriOpcode(Uses64BitFramePtr, Val);
MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(AndOp), Reg)
.addReg(Reg)
.addImm(Val)
.setMIFlag(MachineInstr::FrameSetup);
// The EFLAGS implicit def is dead.
MI->getOperand(3).setIsDead();
}
/// emitPrologue - Push callee-saved registers onto the stack, which
/// automatically adjust the stack pointer. Adjust the stack pointer to allocate
/// space for local variables. Also emit labels used by the exception handler to
/// generate the exception handling frames.
/*
Here's a gist of what gets emitted:
; Establish frame pointer, if needed
[if needs FP]
push %rbp
.cfi_def_cfa_offset 16
.cfi_offset %rbp, -16
.seh_pushreg %rpb
mov %rsp, %rbp
.cfi_def_cfa_register %rbp
; Spill general-purpose registers
[for all callee-saved GPRs]
pushq %<reg>
[if not needs FP]
.cfi_def_cfa_offset (offset from RETADDR)
.seh_pushreg %<reg>
; If the required stack alignment > default stack alignment
; rsp needs to be re-aligned. This creates a "re-alignment gap"
; of unknown size in the stack frame.
[if stack needs re-alignment]
and $MASK, %rsp
; Allocate space for locals
[if target is Windows and allocated space > 4096 bytes]
; Windows needs special care for allocations larger
; than one page.
mov $NNN, %rax
call ___chkstk_ms/___chkstk
sub %rax, %rsp
[else]
sub $NNN, %rsp
[if needs FP]
.seh_stackalloc (size of XMM spill slots)
.seh_setframe %rbp, SEHFrameOffset ; = size of all spill slots
[else]
.seh_stackalloc NNN
; Spill XMMs
; Note, that while only Windows 64 ABI specifies XMMs as callee-preserved,
; they may get spilled on any platform, if the current function
; calls @llvm.eh.unwind.init
[if needs FP]
[for all callee-saved XMM registers]
movaps %<xmm reg>, -MMM(%rbp)
[for all callee-saved XMM registers]
.seh_savexmm %<xmm reg>, (-MMM + SEHFrameOffset)
; i.e. the offset relative to (%rbp - SEHFrameOffset)
[else]
[for all callee-saved XMM registers]
movaps %<xmm reg>, KKK(%rsp)
[for all callee-saved XMM registers]
.seh_savexmm %<xmm reg>, KKK
.seh_endprologue
[if needs base pointer]
mov %rsp, %rbx
[if needs to restore base pointer]
mov %rsp, -MMM(%rbp)
; Emit CFI info
[if needs FP]
[for all callee-saved registers]
.cfi_offset %<reg>, (offset from %rbp)
[else]
.cfi_def_cfa_offset (offset from RETADDR)
[for all callee-saved registers]
.cfi_offset %<reg>, (offset from %rsp)
Notes:
- .seh directives are emitted only for Windows 64 ABI
- .cv_fpo directives are emitted on win32 when emitting CodeView
- .cfi directives are emitted for all other ABIs
- for 32-bit code, substitute %e?? registers for %r??
*/
void X86FrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
assert(&STI == &MF.getSubtarget<X86Subtarget>() &&
"MF used frame lowering for wrong subtarget");
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo &MFI = MF.getFrameInfo();
const Function &Fn = MF.getFunction();
MachineModuleInfo &MMI = MF.getMMI();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
uint64_t MaxAlign = calculateMaxStackAlign(MF); // Desired stack alignment.
uint64_t StackSize = MFI.getStackSize(); // Number of bytes to allocate.
bool IsFunclet = MBB.isEHFuncletEntry();
EHPersonality Personality = EHPersonality::Unknown;
if (Fn.hasPersonalityFn())
Personality = classifyEHPersonality(Fn.getPersonalityFn());
bool FnHasClrFunclet =
MF.hasEHFunclets() && Personality == EHPersonality::CoreCLR;
bool IsClrFunclet = IsFunclet && FnHasClrFunclet;
bool HasFP = hasFP(MF);
bool IsWin64CC = STI.isCallingConvWin64(Fn.getCallingConv());
bool IsWin64Prologue = MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
bool NeedsWin64CFI = IsWin64Prologue && Fn.needsUnwindTableEntry();
// FIXME: Emit FPO data for EH funclets.
bool NeedsWinFPO =
!IsFunclet && STI.isTargetWin32() && MMI.getModule()->getCodeViewFlag();
bool NeedsWinCFI = NeedsWin64CFI || NeedsWinFPO;
bool NeedsDwarfCFI =
!IsWin64Prologue && (MMI.hasDebugInfo() || Fn.needsUnwindTableEntry());
unsigned FramePtr = TRI->getFrameRegister(MF);
const unsigned MachineFramePtr =
STI.isTarget64BitILP32()
? getX86SubSuperRegister(FramePtr, 64) : FramePtr;
unsigned BasePtr = TRI->getBaseRegister();
bool HasWinCFI = false;
// Debug location must be unknown since the first debug location is used
// to determine the end of the prologue.
DebugLoc DL;
// Add RETADDR move area to callee saved frame size.
int TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
if (TailCallReturnAddrDelta && IsWin64Prologue)
report_fatal_error("Can't handle guaranteed tail call under win64 yet");
if (TailCallReturnAddrDelta < 0)
X86FI->setCalleeSavedFrameSize(
X86FI->getCalleeSavedFrameSize() - TailCallReturnAddrDelta);
bool UseStackProbe = !STI.getTargetLowering()->getStackProbeSymbolName(MF).empty();
// The default stack probe size is 4096 if the function has no stackprobesize
// attribute.
unsigned StackProbeSize = 4096;
if (Fn.hasFnAttribute("stack-probe-size"))
Fn.getFnAttribute("stack-probe-size")
.getValueAsString()
.getAsInteger(0, StackProbeSize);
// Re-align the stack on 64-bit if the x86-interrupt calling convention is
// used and an error code was pushed, since the x86-64 ABI requires a 16-byte
// stack alignment.
if (Fn.getCallingConv() == CallingConv::X86_INTR && Is64Bit &&
Fn.arg_size() == 2) {
StackSize += 8;
MFI.setStackSize(StackSize);
emitSPUpdate(MBB, MBBI, DL, -8, /*InEpilogue=*/false);
}
// If this is x86-64 and the Red Zone is not disabled, if we are a leaf
// function, and use up to 128 bytes of stack space, don't have a frame
// pointer, calls, or dynamic alloca then we do not need to adjust the
// stack pointer (we fit in the Red Zone). We also check that we don't
// push and pop from the stack.
if (Is64Bit && !Fn.hasFnAttribute(Attribute::NoRedZone) &&
!TRI->needsStackRealignment(MF) &&
!MFI.hasVarSizedObjects() && // No dynamic alloca.
!MFI.adjustsStack() && // No calls.
!UseStackProbe && // No stack probes.
!IsWin64CC && // Win64 has no Red Zone
!MFI.hasCopyImplyingStackAdjustment() && // Don't push and pop.
!MF.shouldSplitStack()) { // Regular stack
uint64_t MinSize = X86FI->getCalleeSavedFrameSize();
if (HasFP) MinSize += SlotSize;
X86FI->setUsesRedZone(MinSize > 0 || StackSize > 0);
StackSize = std::max(MinSize, StackSize > 128 ? StackSize - 128 : 0);
MFI.setStackSize(StackSize);
}
// Insert stack pointer adjustment for later moving of return addr. Only
// applies to tail call optimized functions where the callee argument stack
// size is bigger than the callers.
if (TailCallReturnAddrDelta < 0) {
BuildStackAdjustment(MBB, MBBI, DL, TailCallReturnAddrDelta,
/*InEpilogue=*/false)
.setMIFlag(MachineInstr::FrameSetup);
}
// Mapping for machine moves:
//
// DST: VirtualFP AND
// SRC: VirtualFP => DW_CFA_def_cfa_offset
// ELSE => DW_CFA_def_cfa
//
// SRC: VirtualFP AND
// DST: Register => DW_CFA_def_cfa_register
//
// ELSE
// OFFSET < 0 => DW_CFA_offset_extended_sf
// REG < 64 => DW_CFA_offset + Reg
// ELSE => DW_CFA_offset_extended
uint64_t NumBytes = 0;
int stackGrowth = -SlotSize;
// Find the funclet establisher parameter
unsigned Establisher = X86::NoRegister;
if (IsClrFunclet)
Establisher = Uses64BitFramePtr ? X86::RCX : X86::ECX;
else if (IsFunclet)
Establisher = Uses64BitFramePtr ? X86::RDX : X86::EDX;
if (IsWin64Prologue && IsFunclet && !IsClrFunclet) {
// Immediately spill establisher into the home slot.
// The runtime cares about this.
// MOV64mr %rdx, 16(%rsp)
unsigned MOVmr = Uses64BitFramePtr ? X86::MOV64mr : X86::MOV32mr;
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(MOVmr)), StackPtr, true, 16)
.addReg(Establisher)
.setMIFlag(MachineInstr::FrameSetup);
MBB.addLiveIn(Establisher);
}
if (HasFP) {
assert(MF.getRegInfo().isReserved(MachineFramePtr) && "FP reserved");
// Calculate required stack adjustment.
uint64_t FrameSize = StackSize - SlotSize;
// If required, include space for extra hidden slot for stashing base pointer.
if (X86FI->getRestoreBasePointer())
FrameSize += SlotSize;
NumBytes = FrameSize - X86FI->getCalleeSavedFrameSize();
// Callee-saved registers are pushed on stack before the stack is realigned.
if (TRI->needsStackRealignment(MF) && !IsWin64Prologue)
NumBytes = alignTo(NumBytes, MaxAlign);
// Get the offset of the stack slot for the EBP register, which is
// guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
// Update the frame offset adjustment.
if (!IsFunclet)
MFI.setOffsetAdjustment(-NumBytes);
else
assert(MFI.getOffsetAdjustment() == -(int)NumBytes &&
"should calculate same local variable offset for funclets");
// Save EBP/RBP into the appropriate stack slot.
BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::PUSH64r : X86::PUSH32r))
.addReg(MachineFramePtr, RegState::Kill)
.setMIFlag(MachineInstr::FrameSetup);
if (NeedsDwarfCFI) {
// Mark the place where EBP/RBP was saved.
// Define the current CFA rule to use the provided offset.
assert(StackSize);
BuildCFI(MBB, MBBI, DL,
MCCFIInstruction::createDefCfaOffset(nullptr, 2 * stackGrowth));
// Change the rule for the FramePtr to be an "offset" rule.
unsigned DwarfFramePtr = TRI->getDwarfRegNum(MachineFramePtr, true);
BuildCFI(MBB, MBBI, DL, MCCFIInstruction::createOffset(
nullptr, DwarfFramePtr, 2 * stackGrowth));
}
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_PushReg))
.addImm(FramePtr)
.setMIFlag(MachineInstr::FrameSetup);
}
if (!IsWin64Prologue && !IsFunclet) {
// Update EBP with the new base value.
BuildMI(MBB, MBBI, DL,
TII.get(Uses64BitFramePtr ? X86::MOV64rr : X86::MOV32rr),
FramePtr)
.addReg(StackPtr)
.setMIFlag(MachineInstr::FrameSetup);
if (NeedsDwarfCFI) {
// Mark effective beginning of when frame pointer becomes valid.
// Define the current CFA to use the EBP/RBP register.
unsigned DwarfFramePtr = TRI->getDwarfRegNum(MachineFramePtr, true);
BuildCFI(MBB, MBBI, DL, MCCFIInstruction::createDefCfaRegister(
nullptr, DwarfFramePtr));
}
if (NeedsWinFPO) {
// .cv_fpo_setframe $FramePtr
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_SetFrame))
.addImm(FramePtr)
.addImm(0)
.setMIFlag(MachineInstr::FrameSetup);
}
}
} else {
assert(!IsFunclet && "funclets without FPs not yet implemented");
NumBytes = StackSize - X86FI->getCalleeSavedFrameSize();
}
// For EH funclets, only allocate enough space for outgoing calls. Save the
// NumBytes value that we would've used for the parent frame.
unsigned ParentFrameNumBytes = NumBytes;
if (IsFunclet)
NumBytes = getWinEHFuncletFrameSize(MF);
// Skip the callee-saved push instructions.
bool PushedRegs = false;
int StackOffset = 2 * stackGrowth;
while (MBBI != MBB.end() &&
MBBI->getFlag(MachineInstr::FrameSetup) &&
(MBBI->getOpcode() == X86::PUSH32r ||
MBBI->getOpcode() == X86::PUSH64r)) {
PushedRegs = true;
unsigned Reg = MBBI->getOperand(0).getReg();
++MBBI;
if (!HasFP && NeedsDwarfCFI) {
// Mark callee-saved push instruction.
// Define the current CFA rule to use the provided offset.
assert(StackSize);
BuildCFI(MBB, MBBI, DL,
MCCFIInstruction::createDefCfaOffset(nullptr, StackOffset));
StackOffset += stackGrowth;
}
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_PushReg))
.addImm(Reg)
.setMIFlag(MachineInstr::FrameSetup);
}
}
// Realign stack after we pushed callee-saved registers (so that we'll be
// able to calculate their offsets from the frame pointer).
// Don't do this for Win64, it needs to realign the stack after the prologue.
if (!IsWin64Prologue && !IsFunclet && TRI->needsStackRealignment(MF)) {
assert(HasFP && "There should be a frame pointer if stack is realigned.");
BuildStackAlignAND(MBB, MBBI, DL, StackPtr, MaxAlign);
}
// If there is an SUB32ri of ESP immediately before this instruction, merge
// the two. This can be the case when tail call elimination is enabled and
// the callee has more arguments then the caller.
NumBytes -= mergeSPUpdates(MBB, MBBI, true);
// Adjust stack pointer: ESP -= numbytes.
// Windows and cygwin/mingw require a prologue helper routine when allocating
// more than 4K bytes on the stack. Windows uses __chkstk and cygwin/mingw
// uses __alloca. __alloca and the 32-bit version of __chkstk will probe the
// stack and adjust the stack pointer in one go. The 64-bit version of
// __chkstk is only responsible for probing the stack. The 64-bit prologue is
// responsible for adjusting the stack pointer. Touching the stack at 4K
// increments is necessary to ensure that the guard pages used by the OS
// virtual memory manager are allocated in correct sequence.
uint64_t AlignedNumBytes = NumBytes;
if (IsWin64Prologue && !IsFunclet && TRI->needsStackRealignment(MF))
AlignedNumBytes = alignTo(AlignedNumBytes, MaxAlign);
if (AlignedNumBytes >= StackProbeSize && UseStackProbe) {
assert(!X86FI->getUsesRedZone() &&
"The Red Zone is not accounted for in stack probes");
// Check whether EAX is livein for this block.
bool isEAXAlive = isEAXLiveIn(MBB);
if (isEAXAlive) {
if (Is64Bit) {
// Save RAX
BuildMI(MBB, MBBI, DL, TII.get(X86::PUSH64r))
.addReg(X86::RAX, RegState::Kill)
.setMIFlag(MachineInstr::FrameSetup);
} else {
// Save EAX
BuildMI(MBB, MBBI, DL, TII.get(X86::PUSH32r))
.addReg(X86::EAX, RegState::Kill)
.setMIFlag(MachineInstr::FrameSetup);
}
}
if (Is64Bit) {
// Handle the 64-bit Windows ABI case where we need to call __chkstk.
// Function prologue is responsible for adjusting the stack pointer.
int Alloc = isEAXAlive ? NumBytes - 8 : NumBytes;
if (isUInt<32>(Alloc)) {
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addImm(Alloc)
.setMIFlag(MachineInstr::FrameSetup);
} else if (isInt<32>(Alloc)) {
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64ri32), X86::RAX)
.addImm(Alloc)
.setMIFlag(MachineInstr::FrameSetup);
} else {
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64ri), X86::RAX)
.addImm(Alloc)
.setMIFlag(MachineInstr::FrameSetup);
}
} else {
// Allocate NumBytes-4 bytes on stack in case of isEAXAlive.
// We'll also use 4 already allocated bytes for EAX.
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addImm(isEAXAlive ? NumBytes - 4 : NumBytes)
.setMIFlag(MachineInstr::FrameSetup);
}
// Call __chkstk, __chkstk_ms, or __alloca.
emitStackProbe(MF, MBB, MBBI, DL, true);
if (isEAXAlive) {
// Restore RAX/EAX
MachineInstr *MI;
if (Is64Bit)
MI = addRegOffset(BuildMI(MF, DL, TII.get(X86::MOV64rm), X86::RAX),
StackPtr, false, NumBytes - 8);
else
MI = addRegOffset(BuildMI(MF, DL, TII.get(X86::MOV32rm), X86::EAX),
StackPtr, false, NumBytes - 4);
MI->setFlag(MachineInstr::FrameSetup);
MBB.insert(MBBI, MI);
}
} else if (NumBytes) {
emitSPUpdate(MBB, MBBI, DL, -(int64_t)NumBytes, /*InEpilogue=*/false);
}
if (NeedsWinCFI && NumBytes) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_StackAlloc))
.addImm(NumBytes)
.setMIFlag(MachineInstr::FrameSetup);
}
int SEHFrameOffset = 0;
unsigned SPOrEstablisher;
if (IsFunclet) {
if (IsClrFunclet) {
// The establisher parameter passed to a CLR funclet is actually a pointer
// to the (mostly empty) frame of its nearest enclosing funclet; we have
// to find the root function establisher frame by loading the PSPSym from
// the intermediate frame.
unsigned PSPSlotOffset = getPSPSlotOffsetFromSP(MF);
MachinePointerInfo NoInfo;
MBB.addLiveIn(Establisher);
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64rm), Establisher),
Establisher, false, PSPSlotOffset)
.addMemOperand(MF.getMachineMemOperand(
NoInfo, MachineMemOperand::MOLoad, SlotSize, SlotSize));
;
// Save the root establisher back into the current funclet's (mostly
// empty) frame, in case a sub-funclet or the GC needs it.
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64mr)), StackPtr,
false, PSPSlotOffset)
.addReg(Establisher)
.addMemOperand(
MF.getMachineMemOperand(NoInfo, MachineMemOperand::MOStore |
MachineMemOperand::MOVolatile,
SlotSize, SlotSize));
}
SPOrEstablisher = Establisher;
} else {
SPOrEstablisher = StackPtr;
}
if (IsWin64Prologue && HasFP) {
// Set RBP to a small fixed offset from RSP. In the funclet case, we base
// this calculation on the incoming establisher, which holds the value of
// RSP from the parent frame at the end of the prologue.
SEHFrameOffset = calculateSetFPREG(ParentFrameNumBytes);
if (SEHFrameOffset)
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::LEA64r), FramePtr),
SPOrEstablisher, false, SEHFrameOffset);
else
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64rr), FramePtr)
.addReg(SPOrEstablisher);
// If this is not a funclet, emit the CFI describing our frame pointer.
if (NeedsWinCFI && !IsFunclet) {
assert(!NeedsWinFPO && "this setframe incompatible with FPO data");
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_SetFrame))
.addImm(FramePtr)
.addImm(SEHFrameOffset)
.setMIFlag(MachineInstr::FrameSetup);
if (isAsynchronousEHPersonality(Personality))
MF.getWinEHFuncInfo()->SEHSetFrameOffset = SEHFrameOffset;
}
} else if (IsFunclet && STI.is32Bit()) {
// Reset EBP / ESI to something good for funclets.
MBBI = restoreWin32EHStackPointers(MBB, MBBI, DL);
// If we're a catch funclet, we can be returned to via catchret. Save ESP
// into the registration node so that the runtime will restore it for us.
if (!MBB.isCleanupFuncletEntry()) {
assert(Personality == EHPersonality::MSVC_CXX);
unsigned FrameReg;
int FI = MF.getWinEHFuncInfo()->EHRegNodeFrameIndex;
int64_t EHRegOffset = getFrameIndexReference(MF, FI, FrameReg);
// ESP is the first field, so no extra displacement is needed.
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32mr)), FrameReg,
false, EHRegOffset)
.addReg(X86::ESP);
}
}
while (MBBI != MBB.end() && MBBI->getFlag(MachineInstr::FrameSetup)) {
const MachineInstr &FrameInstr = *MBBI;
++MBBI;
if (NeedsWinCFI) {
int FI;
if (unsigned Reg = TII.isStoreToStackSlot(FrameInstr, FI)) {
if (X86::FR64RegClass.contains(Reg)) {
unsigned IgnoredFrameReg;
int Offset = getFrameIndexReference(MF, FI, IgnoredFrameReg);
Offset += SEHFrameOffset;
HasWinCFI = true;
assert(!NeedsWinFPO && "SEH_SaveXMM incompatible with FPO data");
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_SaveXMM))
.addImm(Reg)
.addImm(Offset)
.setMIFlag(MachineInstr::FrameSetup);
}
}
}
}
if (NeedsWinCFI && HasWinCFI)
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_EndPrologue))
.setMIFlag(MachineInstr::FrameSetup);
if (FnHasClrFunclet && !IsFunclet) {
// Save the so-called Initial-SP (i.e. the value of the stack pointer
// immediately after the prolog) into the PSPSlot so that funclets
// and the GC can recover it.
unsigned PSPSlotOffset = getPSPSlotOffsetFromSP(MF);
auto PSPInfo = MachinePointerInfo::getFixedStack(
MF, MF.getWinEHFuncInfo()->PSPSymFrameIdx);
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64mr)), StackPtr, false,
PSPSlotOffset)
.addReg(StackPtr)
.addMemOperand(MF.getMachineMemOperand(
PSPInfo, MachineMemOperand::MOStore | MachineMemOperand::MOVolatile,
SlotSize, SlotSize));
}
// Realign stack after we spilled callee-saved registers (so that we'll be
// able to calculate their offsets from the frame pointer).
// Win64 requires aligning the stack after the prologue.
if (IsWin64Prologue && TRI->needsStackRealignment(MF)) {
assert(HasFP && "There should be a frame pointer if stack is realigned.");
BuildStackAlignAND(MBB, MBBI, DL, SPOrEstablisher, MaxAlign);
}
// We already dealt with stack realignment and funclets above.
if (IsFunclet && STI.is32Bit())
return;
// If we need a base pointer, set it up here. It's whatever the value
// of the stack pointer is at this point. Any variable size objects
// will be allocated after this, so we can still use the base pointer
// to reference locals.
if (TRI->hasBasePointer(MF)) {
// Update the base pointer with the current stack pointer.
unsigned Opc = Uses64BitFramePtr ? X86::MOV64rr : X86::MOV32rr;
BuildMI(MBB, MBBI, DL, TII.get(Opc), BasePtr)
.addReg(SPOrEstablisher)
.setMIFlag(MachineInstr::FrameSetup);
if (X86FI->getRestoreBasePointer()) {
// Stash value of base pointer. Saving RSP instead of EBP shortens
// dependence chain. Used by SjLj EH.
unsigned Opm = Uses64BitFramePtr ? X86::MOV64mr : X86::MOV32mr;
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opm)),
FramePtr, true, X86FI->getRestoreBasePointerOffset())
.addReg(SPOrEstablisher)
.setMIFlag(MachineInstr::FrameSetup);
}
if (X86FI->getHasSEHFramePtrSave() && !IsFunclet) {
// Stash the value of the frame pointer relative to the base pointer for
// Win32 EH. This supports Win32 EH, which does the inverse of the above:
// it recovers the frame pointer from the base pointer rather than the
// other way around.
unsigned Opm = Uses64BitFramePtr ? X86::MOV64mr : X86::MOV32mr;
unsigned UsedReg;
int Offset =
getFrameIndexReference(MF, X86FI->getSEHFramePtrSaveIndex(), UsedReg);
assert(UsedReg == BasePtr);
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opm)), UsedReg, true, Offset)
.addReg(FramePtr)
.setMIFlag(MachineInstr::FrameSetup);
}
}
if (((!HasFP && NumBytes) || PushedRegs) && NeedsDwarfCFI) {
// Mark end of stack pointer adjustment.
if (!HasFP && NumBytes) {
// Define the current CFA rule to use the provided offset.
assert(StackSize);
BuildCFI(MBB, MBBI, DL, MCCFIInstruction::createDefCfaOffset(
nullptr, -StackSize + stackGrowth));
}
// Emit DWARF info specifying the offsets of the callee-saved registers.
emitCalleeSavedFrameMoves(MBB, MBBI, DL);
}
// X86 Interrupt handling function cannot assume anything about the direction
// flag (DF in EFLAGS register). Clear this flag by creating "cld" instruction
// in each prologue of interrupt handler function.
//
// FIXME: Create "cld" instruction only in these cases:
// 1. The interrupt handling function uses any of the "rep" instructions.
// 2. Interrupt handling function calls another function.
//
if (Fn.getCallingConv() == CallingConv::X86_INTR)
BuildMI(MBB, MBBI, DL, TII.get(X86::CLD))
.setMIFlag(MachineInstr::FrameSetup);
// At this point we know if the function has WinCFI or not.
MF.setHasWinCFI(HasWinCFI);
}
bool X86FrameLowering::canUseLEAForSPInEpilogue(
const MachineFunction &MF) const {
// We can't use LEA instructions for adjusting the stack pointer if we don't
// have a frame pointer in the Win64 ABI. Only ADD instructions may be used
// to deallocate the stack.
// This means that we can use LEA for SP in two situations:
// 1. We *aren't* using the Win64 ABI which means we are free to use LEA.
// 2. We *have* a frame pointer which means we are permitted to use LEA.
return !MF.getTarget().getMCAsmInfo()->usesWindowsCFI() || hasFP(MF);
}
static bool isFuncletReturnInstr(MachineInstr &MI) {
switch (MI.getOpcode()) {
case X86::CATCHRET:
case X86::CLEANUPRET:
return true;
default:
return false;
}
llvm_unreachable("impossible");
}
// CLR funclets use a special "Previous Stack Pointer Symbol" slot on the
// stack. It holds a pointer to the bottom of the root function frame. The
// establisher frame pointer passed to a nested funclet may point to the
// (mostly empty) frame of its parent funclet, but it will need to find
// the frame of the root function to access locals. To facilitate this,
// every funclet copies the pointer to the bottom of the root function
// frame into a PSPSym slot in its own (mostly empty) stack frame. Using the
// same offset for the PSPSym in the root function frame that's used in the
// funclets' frames allows each funclet to dynamically accept any ancestor
// frame as its establisher argument (the runtime doesn't guarantee the
// immediate parent for some reason lost to history), and also allows the GC,
// which uses the PSPSym for some bookkeeping, to find it in any funclet's
// frame with only a single offset reported for the entire method.
unsigned
X86FrameLowering::getPSPSlotOffsetFromSP(const MachineFunction &MF) const {
const WinEHFuncInfo &Info = *MF.getWinEHFuncInfo();
unsigned SPReg;
int Offset = getFrameIndexReferencePreferSP(MF, Info.PSPSymFrameIdx, SPReg,
/*IgnoreSPUpdates*/ true);
assert(Offset >= 0 && SPReg == TRI->getStackRegister());
return static_cast<unsigned>(Offset);
}
unsigned
X86FrameLowering::getWinEHFuncletFrameSize(const MachineFunction &MF) const {
// This is the size of the pushed CSRs.
unsigned CSSize =
MF.getInfo<X86MachineFunctionInfo>()->getCalleeSavedFrameSize();
// This is the amount of stack a funclet needs to allocate.
unsigned UsedSize;
EHPersonality Personality =
classifyEHPersonality(MF.getFunction().getPersonalityFn());
if (Personality == EHPersonality::CoreCLR) {
// CLR funclets need to hold enough space to include the PSPSym, at the
// same offset from the stack pointer (immediately after the prolog) as it
// resides at in the main function.
UsedSize = getPSPSlotOffsetFromSP(MF) + SlotSize;
} else {
// Other funclets just need enough stack for outgoing call arguments.
UsedSize = MF.getFrameInfo().getMaxCallFrameSize();
}
// RBP is not included in the callee saved register block. After pushing RBP,
// everything is 16 byte aligned. Everything we allocate before an outgoing
// call must also be 16 byte aligned.
unsigned FrameSizeMinusRBP = alignTo(CSSize + UsedSize, getStackAlignment());
// Subtract out the size of the callee saved registers. This is how much stack
// each funclet will allocate.
return FrameSizeMinusRBP - CSSize;
}
static bool isTailCallOpcode(unsigned Opc) {
return Opc == X86::TCRETURNri || Opc == X86::TCRETURNdi ||
Opc == X86::TCRETURNmi ||
Opc == X86::TCRETURNri64 || Opc == X86::TCRETURNdi64 ||
Opc == X86::TCRETURNmi64;
}
void X86FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
MachineBasicBlock::iterator Terminator = MBB.getFirstTerminator();
MachineBasicBlock::iterator MBBI = Terminator;
DebugLoc DL;
if (MBBI != MBB.end())
DL = MBBI->getDebugLoc();
// standard x86_64 and NaCl use 64-bit frame/stack pointers, x32 - 32-bit.
const bool Is64BitILP32 = STI.isTarget64BitILP32();
unsigned FramePtr = TRI->getFrameRegister(MF);
unsigned MachineFramePtr =
Is64BitILP32 ? getX86SubSuperRegister(FramePtr, 64) : FramePtr;
bool IsWin64Prologue = MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
bool NeedsWin64CFI =
IsWin64Prologue && MF.getFunction().needsUnwindTableEntry();
bool IsFunclet = MBBI == MBB.end() ? false : isFuncletReturnInstr(*MBBI);
// Get the number of bytes to allocate from the FrameInfo.
uint64_t StackSize = MFI.getStackSize();
uint64_t MaxAlign = calculateMaxStackAlign(MF);
unsigned CSSize = X86FI->getCalleeSavedFrameSize();
bool HasFP = hasFP(MF);
uint64_t NumBytes = 0;
if (IsFunclet) {
assert(HasFP && "EH funclets without FP not yet implemented");
NumBytes = getWinEHFuncletFrameSize(MF);
} else if (HasFP) {
// Calculate required stack adjustment.
uint64_t FrameSize = StackSize - SlotSize;
NumBytes = FrameSize - CSSize;
// Callee-saved registers were pushed on stack before the stack was
// realigned.
if (TRI->needsStackRealignment(MF) && !IsWin64Prologue)
NumBytes = alignTo(FrameSize, MaxAlign);
} else {
NumBytes = StackSize - CSSize;
}
uint64_t SEHStackAllocAmt = NumBytes;
if (HasFP) {
// Pop EBP.
BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::POP64r : X86::POP32r),
MachineFramePtr)
.setMIFlag(MachineInstr::FrameDestroy);
}
MachineBasicBlock::iterator FirstCSPop = MBBI;
// Skip the callee-saved pop instructions.
while (MBBI != MBB.begin()) {
MachineBasicBlock::iterator PI = std::prev(MBBI);
unsigned Opc = PI->getOpcode();
if (Opc != X86::DBG_VALUE && !PI->isTerminator()) {
if ((Opc != X86::POP32r || !PI->getFlag(MachineInstr::FrameDestroy)) &&
(Opc != X86::POP64r || !PI->getFlag(MachineInstr::FrameDestroy)))
break;
FirstCSPop = PI;
}
--MBBI;
}
MBBI = FirstCSPop;
if (IsFunclet && Terminator->getOpcode() == X86::CATCHRET)
emitCatchRetReturnValue(MBB, FirstCSPop, &*Terminator);
if (MBBI != MBB.end())
DL = MBBI->getDebugLoc();
// If there is an ADD32ri or SUB32ri of ESP immediately before this
// instruction, merge the two instructions.
if (NumBytes || MFI.hasVarSizedObjects())
NumBytes += mergeSPUpdates(MBB, MBBI, true);
// If dynamic alloca is used, then reset esp to point to the last callee-saved
// slot before popping them off! Same applies for the case, when stack was
// realigned. Don't do this if this was a funclet epilogue, since the funclets
// will not do realignment or dynamic stack allocation.
if ((TRI->needsStackRealignment(MF) || MFI.hasVarSizedObjects()) &&
!IsFunclet) {
if (TRI->needsStackRealignment(MF))
MBBI = FirstCSPop;
unsigned SEHFrameOffset = calculateSetFPREG(SEHStackAllocAmt);
uint64_t LEAAmount =
IsWin64Prologue ? SEHStackAllocAmt - SEHFrameOffset : -CSSize;
// There are only two legal forms of epilogue:
// - add SEHAllocationSize, %rsp
// - lea SEHAllocationSize(%FramePtr), %rsp
//
// 'mov %FramePtr, %rsp' will not be recognized as an epilogue sequence.
// However, we may use this sequence if we have a frame pointer because the
// effects of the prologue can safely be undone.
if (LEAAmount != 0) {
unsigned Opc = getLEArOpcode(Uses64BitFramePtr);
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr),
FramePtr, false, LEAAmount);
--MBBI;
} else {
unsigned Opc = (Uses64BitFramePtr ? X86::MOV64rr : X86::MOV32rr);
BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr)
.addReg(FramePtr);
--MBBI;
}
} else if (NumBytes) {
// Adjust stack pointer back: ESP += numbytes.
emitSPUpdate(MBB, MBBI, DL, NumBytes, /*InEpilogue=*/true);
--MBBI;
}
// Windows unwinder will not invoke function's exception handler if IP is
// either in prologue or in epilogue. This behavior causes a problem when a
// call immediately precedes an epilogue, because the return address points
// into the epilogue. To cope with that, we insert an epilogue marker here,
// then replace it with a 'nop' if it ends up immediately after a CALL in the
// final emitted code.
if (NeedsWin64CFI && MF.hasWinCFI())
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_Epilogue));
if (Terminator == MBB.end() || !isTailCallOpcode(Terminator->getOpcode())) {
// Add the return addr area delta back since we are not tail calling.
int Offset = -1 * X86FI->getTCReturnAddrDelta();
assert(Offset >= 0 && "TCDelta should never be positive");
if (Offset) {
// Check for possible merge with preceding ADD instruction.
Offset += mergeSPUpdates(MBB, Terminator, true);
emitSPUpdate(MBB, Terminator, DL, Offset, /*InEpilogue=*/true);
}
}
}
int X86FrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
unsigned &FrameReg) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
bool IsFixed = MFI.isFixedObjectIndex(FI);
// We can't calculate offset from frame pointer if the stack is realigned,
// so enforce usage of stack/base pointer. The base pointer is used when we
// have dynamic allocas in addition to dynamic realignment.
if (TRI->hasBasePointer(MF))
FrameReg = IsFixed ? TRI->getFramePtr() : TRI->getBaseRegister();
else if (TRI->needsStackRealignment(MF))
FrameReg = IsFixed ? TRI->getFramePtr() : TRI->getStackRegister();
else
FrameReg = TRI->getFrameRegister(MF);
// Offset will hold the offset from the stack pointer at function entry to the
// object.
// We need to factor in additional offsets applied during the prologue to the
// frame, base, and stack pointer depending on which is used.
int Offset = MFI.getObjectOffset(FI) - getOffsetOfLocalArea();
const X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
unsigned CSSize = X86FI->getCalleeSavedFrameSize();
uint64_t StackSize = MFI.getStackSize();
bool HasFP = hasFP(MF);
bool IsWin64Prologue = MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
int64_t FPDelta = 0;
if (IsWin64Prologue) {
assert(!MFI.hasCalls() || (StackSize % 16) == 8);
// Calculate required stack adjustment.
uint64_t FrameSize = StackSize - SlotSize;
// If required, include space for extra hidden slot for stashing base pointer.
if (X86FI->getRestoreBasePointer())
FrameSize += SlotSize;
uint64_t NumBytes = FrameSize - CSSize;
uint64_t SEHFrameOffset = calculateSetFPREG(NumBytes);
if (FI && FI == X86FI->getFAIndex())
return -SEHFrameOffset;
// FPDelta is the offset from the "traditional" FP location of the old base
// pointer followed by return address and the location required by the
// restricted Win64 prologue.
// Add FPDelta to all offsets below that go through the frame pointer.
FPDelta = FrameSize - SEHFrameOffset;
assert((!MFI.hasCalls() || (FPDelta % 16) == 0) &&
"FPDelta isn't aligned per the Win64 ABI!");
}
if (TRI->hasBasePointer(MF)) {
assert(HasFP && "VLAs and dynamic stack realign, but no FP?!");
if (FI < 0) {
// Skip the saved EBP.
return Offset + SlotSize + FPDelta;
} else {
assert((-(Offset + StackSize)) % MFI.getObjectAlignment(FI) == 0);
return Offset + StackSize;
}
} else if (TRI->needsStackRealignment(MF)) {
if (FI < 0) {
// Skip the saved EBP.
return Offset + SlotSize + FPDelta;
} else {
assert((-(Offset + StackSize)) % MFI.getObjectAlignment(FI) == 0);
return Offset + StackSize;
}
// FIXME: Support tail calls
} else {
if (!HasFP)
return Offset + StackSize;
// Skip the saved EBP.
Offset += SlotSize;
// Skip the RETADDR move area
int TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
if (TailCallReturnAddrDelta < 0)
Offset -= TailCallReturnAddrDelta;
}
return Offset + FPDelta;
}
int X86FrameLowering::getFrameIndexReferenceSP(const MachineFunction &MF,
int FI, unsigned &FrameReg,
int Adjustment) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
FrameReg = TRI->getStackRegister();
return MFI.getObjectOffset(FI) - getOffsetOfLocalArea() + Adjustment;
}
int
X86FrameLowering::getFrameIndexReferencePreferSP(const MachineFunction &MF,
int FI, unsigned &FrameReg,
bool IgnoreSPUpdates) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
// Does not include any dynamic realign.
const uint64_t StackSize = MFI.getStackSize();
// LLVM arranges the stack as follows:
// ...
// ARG2
// ARG1
// RETADDR
// PUSH RBP <-- RBP points here
// PUSH CSRs
// ~~~~~~~ <-- possible stack realignment (non-win64)
// ...
// STACK OBJECTS
// ... <-- RSP after prologue points here
// ~~~~~~~ <-- possible stack realignment (win64)
//
// if (hasVarSizedObjects()):
// ... <-- "base pointer" (ESI/RBX) points here
// DYNAMIC ALLOCAS
// ... <-- RSP points here
//
// Case 1: In the simple case of no stack realignment and no dynamic
// allocas, both "fixed" stack objects (arguments and CSRs) are addressable
// with fixed offsets from RSP.
//
// Case 2: In the case of stack realignment with no dynamic allocas, fixed
// stack objects are addressed with RBP and regular stack objects with RSP.
//
// Case 3: In the case of dynamic allocas and stack realignment, RSP is used
// to address stack arguments for outgoing calls and nothing else. The "base
// pointer" points to local variables, and RBP points to fixed objects.
//
// In cases 2 and 3, we can only answer for non-fixed stack objects, and the
// answer we give is relative to the SP after the prologue, and not the
// SP in the middle of the function.
if (MFI.isFixedObjectIndex(FI) && TRI->needsStackRealignment(MF) &&
!STI.isTargetWin64())
return getFrameIndexReference(MF, FI, FrameReg);
// If !hasReservedCallFrame the function might have SP adjustement in the
// body. So, even though the offset is statically known, it depends on where
// we are in the function.
const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
if (!IgnoreSPUpdates && !TFI->hasReservedCallFrame(MF))
return getFrameIndexReference(MF, FI, FrameReg);
// We don't handle tail calls, and shouldn't be seeing them either.
assert(MF.getInfo<X86MachineFunctionInfo>()->getTCReturnAddrDelta() >= 0 &&
"we don't handle this case!");
// This is how the math works out:
//
// %rsp grows (i.e. gets lower) left to right. Each box below is
// one word (eight bytes). Obj0 is the stack slot we're trying to
// get to.
//
// ----------------------------------
// | BP | Obj0 | Obj1 | ... | ObjN |
// ----------------------------------
// ^ ^ ^ ^
// A B C E
//
// A is the incoming stack pointer.
// (B - A) is the local area offset (-8 for x86-64) [1]
// (C - A) is the Offset returned by MFI.getObjectOffset for Obj0 [2]
//
// |(E - B)| is the StackSize (absolute value, positive). For a
// stack that grown down, this works out to be (B - E). [3]
//
// E is also the value of %rsp after stack has been set up, and we
// want (C - E) -- the value we can add to %rsp to get to Obj0. Now
// (C - E) == (C - A) - (B - A) + (B - E)
// { Using [1], [2] and [3] above }
// == getObjectOffset - LocalAreaOffset + StackSize
return getFrameIndexReferenceSP(MF, FI, FrameReg, StackSize);
}
bool X86FrameLowering::assignCalleeSavedSpillSlots(
MachineFunction &MF, const TargetRegisterInfo *TRI,
std::vector<CalleeSavedInfo> &CSI) const {
MachineFrameInfo &MFI = MF.getFrameInfo();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
unsigned CalleeSavedFrameSize = 0;
int SpillSlotOffset = getOffsetOfLocalArea() + X86FI->getTCReturnAddrDelta();
int64_t TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
if (TailCallReturnAddrDelta < 0) {
// create RETURNADDR area
// arg
// arg
// RETADDR
// { ...
// RETADDR area
// ...
// }
// [EBP]
MFI.CreateFixedObject(-TailCallReturnAddrDelta,
TailCallReturnAddrDelta - SlotSize, true);
}
// Spill the BasePtr if it's used.
if (this->TRI->hasBasePointer(MF)) {
// Allocate a spill slot for EBP if we have a base pointer and EH funclets.
if (MF.hasEHFunclets()) {
int FI = MFI.CreateSpillStackObject(SlotSize, SlotSize);
X86FI->setHasSEHFramePtrSave(true);
X86FI->setSEHFramePtrSaveIndex(FI);
}
}
if (hasFP(MF)) {
// emitPrologue always spills frame register the first thing.
SpillSlotOffset -= SlotSize;
MFI.CreateFixedSpillStackObject(SlotSize, SpillSlotOffset);
// Since emitPrologue and emitEpilogue will handle spilling and restoring of
// the frame register, we can delete it from CSI list and not have to worry
// about avoiding it later.
unsigned FPReg = TRI->getFrameRegister(MF);
for (unsigned i = 0; i < CSI.size(); ++i) {
if (TRI->regsOverlap(CSI[i].getReg(),FPReg)) {
CSI.erase(CSI.begin() + i);
break;
}
}
}
// Assign slots for GPRs. It increases frame size.
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i - 1].getReg();
if (!X86::GR64RegClass.contains(Reg) && !X86::GR32RegClass.contains(Reg))
continue;
SpillSlotOffset -= SlotSize;
CalleeSavedFrameSize += SlotSize;
int SlotIndex = MFI.CreateFixedSpillStackObject(SlotSize, SpillSlotOffset);
CSI[i - 1].setFrameIdx(SlotIndex);
}
X86FI->setCalleeSavedFrameSize(CalleeSavedFrameSize);
// Assign slots for XMMs.
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i - 1].getReg();
if (X86::GR64RegClass.contains(Reg) || X86::GR32RegClass.contains(Reg))
continue;
// If this is k-register make sure we lookup via the largest legal type.
MVT VT = MVT::Other;
if (X86::VK16RegClass.contains(Reg))
VT = STI.hasBWI() ? MVT::v64i1 : MVT::v16i1;
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg, VT);
unsigned Size = TRI->getSpillSize(*RC);
unsigned Align = TRI->getSpillAlignment(*RC);
// ensure alignment
SpillSlotOffset -= std::abs(SpillSlotOffset) % Align;
// spill into slot
SpillSlotOffset -= Size;
int SlotIndex = MFI.CreateFixedSpillStackObject(Size, SpillSlotOffset);
CSI[i - 1].setFrameIdx(SlotIndex);
MFI.ensureMaxAlignment(Align);
}
return true;
}
bool X86FrameLowering::spillCalleeSavedRegisters(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
DebugLoc DL = MBB.findDebugLoc(MI);
// Don't save CSRs in 32-bit EH funclets. The caller saves EBX, EBP, ESI, EDI
// for us, and there are no XMM CSRs on Win32.
if (MBB.isEHFuncletEntry() && STI.is32Bit() && STI.isOSWindows())
return true;
// Push GPRs. It increases frame size.
const MachineFunction &MF = *MBB.getParent();
unsigned Opc = STI.is64Bit() ? X86::PUSH64r : X86::PUSH32r;
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i - 1].getReg();
if (!X86::GR64RegClass.contains(Reg) && !X86::GR32RegClass.contains(Reg))
continue;
const MachineRegisterInfo &MRI = MF.getRegInfo();
bool isLiveIn = MRI.isLiveIn(Reg);
if (!isLiveIn)
MBB.addLiveIn(Reg);
// Decide whether we can add a kill flag to the use.
bool CanKill = !isLiveIn;
// Check if any subregister is live-in
if (CanKill) {
for (MCRegAliasIterator AReg(Reg, TRI, false); AReg.isValid(); ++AReg) {
if (MRI.isLiveIn(*AReg)) {
CanKill = false;
break;
}
}
}
// Do not set a kill flag on values that are also marked as live-in. This
// happens with the @llvm-returnaddress intrinsic and with arguments
// passed in callee saved registers.
// Omitting the kill flags is conservatively correct even if the live-in
// is not used after all.
BuildMI(MBB, MI, DL, TII.get(Opc)).addReg(Reg, getKillRegState(CanKill))
.setMIFlag(MachineInstr::FrameSetup);
}
// Make XMM regs spilled. X86 does not have ability of push/pop XMM.
// It can be done by spilling XMMs to stack frame.
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (X86::GR64RegClass.contains(Reg) || X86::GR32RegClass.contains(Reg))
continue;
// If this is k-register make sure we lookup via the largest legal type.
MVT VT = MVT::Other;
if (X86::VK16RegClass.contains(Reg))
VT = STI.hasBWI() ? MVT::v64i1 : MVT::v16i1;
// Add the callee-saved register as live-in. It's killed at the spill.
MBB.addLiveIn(Reg);
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg, VT);
TII.storeRegToStackSlot(MBB, MI, Reg, true, CSI[i - 1].getFrameIdx(), RC,
TRI);
--MI;
MI->setFlag(MachineInstr::FrameSetup);
++MI;
}
return true;
}
void X86FrameLowering::emitCatchRetReturnValue(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
MachineInstr *CatchRet) const {
// SEH shouldn't use catchret.
assert(!isAsynchronousEHPersonality(classifyEHPersonality(
MBB.getParent()->getFunction().getPersonalityFn())) &&
"SEH should not use CATCHRET");
DebugLoc DL = CatchRet->getDebugLoc();
MachineBasicBlock *CatchRetTarget = CatchRet->getOperand(0).getMBB();
// Fill EAX/RAX with the address of the target block.
if (STI.is64Bit()) {
// LEA64r CatchRetTarget(%rip), %rax
BuildMI(MBB, MBBI, DL, TII.get(X86::LEA64r), X86::RAX)
.addReg(X86::RIP)
.addImm(0)
.addReg(0)
.addMBB(CatchRetTarget)
.addReg(0);
} else {
// MOV32ri $CatchRetTarget, %eax
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addMBB(CatchRetTarget);
}
// Record that we've taken the address of CatchRetTarget and no longer just
// reference it in a terminator.
CatchRetTarget->setHasAddressTaken();
}
bool X86FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
if (MI != MBB.end() && isFuncletReturnInstr(*MI) && STI.isOSWindows()) {
// Don't restore CSRs in 32-bit EH funclets. Matches
// spillCalleeSavedRegisters.
if (STI.is32Bit())
return true;
// Don't restore CSRs before an SEH catchret. SEH except blocks do not form
// funclets. emitEpilogue transforms these to normal jumps.
if (MI->getOpcode() == X86::CATCHRET) {
const Function &F = MBB.getParent()->getFunction();
bool IsSEH = isAsynchronousEHPersonality(
classifyEHPersonality(F.getPersonalityFn()));
if (IsSEH)
return true;
}
}
DebugLoc DL = MBB.findDebugLoc(MI);
// Reload XMMs from stack frame.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
if (X86::GR64RegClass.contains(Reg) ||
X86::GR32RegClass.contains(Reg))
continue;
// If this is k-register make sure we lookup via the largest legal type.
MVT VT = MVT::Other;
if (X86::VK16RegClass.contains(Reg))
VT = STI.hasBWI() ? MVT::v64i1 : MVT::v16i1;
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg, VT);
TII.loadRegFromStackSlot(MBB, MI, Reg, CSI[i].getFrameIdx(), RC, TRI);
}
// POP GPRs.
unsigned Opc = STI.is64Bit() ? X86::POP64r : X86::POP32r;
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
if (!X86::GR64RegClass.contains(Reg) &&
!X86::GR32RegClass.contains(Reg))
continue;
BuildMI(MBB, MI, DL, TII.get(Opc), Reg)
.setMIFlag(MachineInstr::FrameDestroy);
}
return true;
}
void X86FrameLowering::determineCalleeSaves(MachineFunction &MF,
BitVector &SavedRegs,
RegScavenger *RS) const {
TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
// Spill the BasePtr if it's used.
if (TRI->hasBasePointer(MF)){
unsigned BasePtr = TRI->getBaseRegister();
if (STI.isTarget64BitILP32())
BasePtr = getX86SubSuperRegister(BasePtr, 64);
SavedRegs.set(BasePtr);
}
}
static bool
HasNestArgument(const MachineFunction *MF) {
const Function &F = MF->getFunction();
for (Function::const_arg_iterator I = F.arg_begin(), E = F.arg_end();
I != E; I++) {
if (I->hasNestAttr())
return true;
}
return false;
}
/// GetScratchRegister - Get a temp register for performing work in the
/// segmented stack and the Erlang/HiPE stack prologue. Depending on platform
/// and the properties of the function either one or two registers will be
/// needed. Set primary to true for the first register, false for the second.
static unsigned
GetScratchRegister(bool Is64Bit, bool IsLP64, const MachineFunction &MF, bool Primary) {
CallingConv::ID CallingConvention = MF.getFunction().getCallingConv();
// Erlang stuff.
if (CallingConvention == CallingConv::HiPE) {
if (Is64Bit)
return Primary ? X86::R14 : X86::R13;
else
return Primary ? X86::EBX : X86::EDI;
}
if (Is64Bit) {
if (IsLP64)
return Primary ? X86::R11 : X86::R12;
else
return Primary ? X86::R11D : X86::R12D;
}
bool IsNested = HasNestArgument(&MF);
if (CallingConvention == CallingConv::X86_FastCall ||
CallingConvention == CallingConv::Fast) {
if (IsNested)
report_fatal_error("Segmented stacks does not support fastcall with "
"nested function.");
return Primary ? X86::EAX : X86::ECX;
}
if (IsNested)
return Primary ? X86::EDX : X86::EAX;
return Primary ? X86::ECX : X86::EAX;
}
// The stack limit in the TCB is set to this many bytes above the actual stack
// limit.
static const uint64_t kSplitStackAvailable = 256;
void X86FrameLowering::adjustForSegmentedStacks(
MachineFunction &MF, MachineBasicBlock &PrologueMBB) const {
MachineFrameInfo &MFI = MF.getFrameInfo();
uint64_t StackSize;
unsigned TlsReg, TlsOffset;
DebugLoc DL;
// To support shrink-wrapping we would need to insert the new blocks
// at the right place and update the branches to PrologueMBB.
assert(&(*MF.begin()) == &PrologueMBB && "Shrink-wrapping not supported yet");
unsigned ScratchReg = GetScratchRegister(Is64Bit, IsLP64, MF, true);
assert(!MF.getRegInfo().isLiveIn(ScratchReg) &&
"Scratch register is live-in");
if (MF.getFunction().isVarArg())
report_fatal_error("Segmented stacks do not support vararg functions.");
if (!STI.isTargetLinux() && !STI.isTargetDarwin() && !STI.isTargetWin32() &&
!STI.isTargetWin64() && !STI.isTargetFreeBSD() &&
!STI.isTargetDragonFly())
report_fatal_error("Segmented stacks not supported on this platform.");
// Eventually StackSize will be calculated by a link-time pass; which will
// also decide whether checking code needs to be injected into this particular
// prologue.
StackSize = MFI.getStackSize();
// Do not generate a prologue for functions with a stack of size zero
if (StackSize == 0)
return;
MachineBasicBlock *allocMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *checkMBB = MF.CreateMachineBasicBlock();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
bool IsNested = false;
// We need to know if the function has a nest argument only in 64 bit mode.
if (Is64Bit)
IsNested = HasNestArgument(&MF);
// The MOV R10, RAX needs to be in a different block, since the RET we emit in
// allocMBB needs to be last (terminating) instruction.
for (const auto &LI : PrologueMBB.liveins()) {
allocMBB->addLiveIn(LI);
checkMBB->addLiveIn(LI);
}
if (IsNested)
allocMBB->addLiveIn(IsLP64 ? X86::R10 : X86::R10D);
MF.push_front(allocMBB);
MF.push_front(checkMBB);
// When the frame size is less than 256 we just compare the stack
// boundary directly to the value of the stack pointer, per gcc.
bool CompareStackPointer = StackSize < kSplitStackAvailable;
// Read the limit off the current stacklet off the stack_guard location.
if (Is64Bit) {
if (STI.isTargetLinux()) {
TlsReg = X86::FS;
TlsOffset = IsLP64 ? 0x70 : 0x40;
} else if (STI.isTargetDarwin()) {
TlsReg = X86::GS;
TlsOffset = 0x60 + 90*8; // See pthread_machdep.h. Steal TLS slot 90.
} else if (STI.isTargetWin64()) {
TlsReg = X86::GS;
TlsOffset = 0x28; // pvArbitrary, reserved for application use
} else if (STI.isTargetFreeBSD()) {
TlsReg = X86::FS;
TlsOffset = 0x18;
} else if (STI.isTargetDragonFly()) {
TlsReg = X86::FS;
TlsOffset = 0x20; // use tls_tcb.tcb_segstack
} else {
report_fatal_error("Segmented stacks not supported on this platform.");
}
if (CompareStackPointer)
ScratchReg = IsLP64 ? X86::RSP : X86::ESP;
else
BuildMI(checkMBB, DL, TII.get(IsLP64 ? X86::LEA64r : X86::LEA64_32r), ScratchReg).addReg(X86::RSP)
.addImm(1).addReg(0).addImm(-StackSize).addReg(0);
BuildMI(checkMBB, DL, TII.get(IsLP64 ? X86::CMP64rm : X86::CMP32rm)).addReg(ScratchReg)
.addReg(0).addImm(1).addReg(0).addImm(TlsOffset).addReg(TlsReg);
} else {
if (STI.isTargetLinux()) {
TlsReg = X86::GS;
TlsOffset = 0x30;
} else if (STI.isTargetDarwin()) {
TlsReg = X86::GS;
TlsOffset = 0x48 + 90*4;
} else if (STI.isTargetWin32()) {
TlsReg = X86::FS;
TlsOffset = 0x14; // pvArbitrary, reserved for application use
} else if (STI.isTargetDragonFly()) {
TlsReg = X86::FS;
TlsOffset = 0x10; // use tls_tcb.tcb_segstack
} else if (STI.isTargetFreeBSD()) {
report_fatal_error("Segmented stacks not supported on FreeBSD i386.");
} else {
report_fatal_error("Segmented stacks not supported on this platform.");
}
if (CompareStackPointer)
ScratchReg = X86::ESP;
else
BuildMI(checkMBB, DL, TII.get(X86::LEA32r), ScratchReg).addReg(X86::ESP)
.addImm(1).addReg(0).addImm(-StackSize).addReg(0);
if (STI.isTargetLinux() || STI.isTargetWin32() || STI.isTargetWin64() ||
STI.isTargetDragonFly()) {
BuildMI(checkMBB, DL, TII.get(X86::CMP32rm)).addReg(ScratchReg)
.addReg(0).addImm(0).addReg(0).addImm(TlsOffset).addReg(TlsReg);
} else if (STI.isTargetDarwin()) {
// TlsOffset doesn't fit into a mod r/m byte so we need an extra register.
unsigned ScratchReg2;
bool SaveScratch2;
if (CompareStackPointer) {
// The primary scratch register is available for holding the TLS offset.
ScratchReg2 = GetScratchRegister(Is64Bit, IsLP64, MF, true);
SaveScratch2 = false;
} else {
// Need to use a second register to hold the TLS offset
ScratchReg2 = GetScratchRegister(Is64Bit, IsLP64, MF, false);
// Unfortunately, with fastcc the second scratch register may hold an
// argument.
SaveScratch2 = MF.getRegInfo().isLiveIn(ScratchReg2);
}
// If Scratch2 is live-in then it needs to be saved.
assert((!MF.getRegInfo().isLiveIn(ScratchReg2) || SaveScratch2) &&
"Scratch register is live-in and not saved");
if (SaveScratch2)
BuildMI(checkMBB, DL, TII.get(X86::PUSH32r))
.addReg(ScratchReg2, RegState::Kill);
BuildMI(checkMBB, DL, TII.get(X86::MOV32ri), ScratchReg2)
.addImm(TlsOffset);
BuildMI(checkMBB, DL, TII.get(X86::CMP32rm))
.addReg(ScratchReg)
.addReg(ScratchReg2).addImm(1).addReg(0)
.addImm(0)
.addReg(TlsReg);
if (SaveScratch2)
BuildMI(checkMBB, DL, TII.get(X86::POP32r), ScratchReg2);
}
}
// This jump is taken if SP >= (Stacklet Limit + Stack Space required).
// It jumps to normal execution of the function body.
BuildMI(checkMBB, DL, TII.get(X86::JA_1)).addMBB(&PrologueMBB);
// On 32 bit we first push the arguments size and then the frame size. On 64
// bit, we pass the stack frame size in r10 and the argument size in r11.
if (Is64Bit) {
// Functions with nested arguments use R10, so it needs to be saved across
// the call to _morestack
const unsigned RegAX = IsLP64 ? X86::RAX : X86::EAX;
const unsigned Reg10 = IsLP64 ? X86::R10 : X86::R10D;
const unsigned Reg11 = IsLP64 ? X86::R11 : X86::R11D;
const unsigned MOVrr = IsLP64 ? X86::MOV64rr : X86::MOV32rr;
const unsigned MOVri = IsLP64 ? X86::MOV64ri : X86::MOV32ri;
if (IsNested)
BuildMI(allocMBB, DL, TII.get(MOVrr), RegAX).addReg(Reg10);
BuildMI(allocMBB, DL, TII.get(MOVri), Reg10)
.addImm(StackSize);
BuildMI(allocMBB, DL, TII.get(MOVri), Reg11)
.addImm(X86FI->getArgumentStackSize());
} else {
BuildMI(allocMBB, DL, TII.get(X86::PUSHi32))
.addImm(X86FI->getArgumentStackSize());
BuildMI(allocMBB, DL, TII.get(X86::PUSHi32))
.addImm(StackSize);
}
// __morestack is in libgcc
if (Is64Bit && MF.getTarget().getCodeModel() == CodeModel::Large) {
// Under the large code model, we cannot assume that __morestack lives
// within 2^31 bytes of the call site, so we cannot use pc-relative
// addressing. We cannot perform the call via a temporary register,
// as the rax register may be used to store the static chain, and all
// other suitable registers may be either callee-save or used for
// parameter passing. We cannot use the stack at this point either
// because __morestack manipulates the stack directly.
//
// To avoid these issues, perform an indirect call via a read-only memory
// location containing the address.
//
// This solution is not perfect, as it assumes that the .rodata section
// is laid out within 2^31 bytes of each function body, but this seems
// to be sufficient for JIT.
// FIXME: Add retpoline support and remove the error here..
if (STI.useRetpoline())
report_fatal_error("Emitting morestack calls on 64-bit with the large "
"code model and retpoline not yet implemented.");
BuildMI(allocMBB, DL, TII.get(X86::CALL64m))
.addReg(X86::RIP)
.addImm(0)
.addReg(0)
.addExternalSymbol("__morestack_addr")
.addReg(0);
MF.getMMI().setUsesMorestackAddr(true);
} else {
if (Is64Bit)
BuildMI(allocMBB, DL, TII.get(X86::CALL64pcrel32))
.addExternalSymbol("__morestack");
else
BuildMI(allocMBB, DL, TII.get(X86::CALLpcrel32))
.addExternalSymbol("__morestack");
}
if (IsNested)
BuildMI(allocMBB, DL, TII.get(X86::MORESTACK_RET_RESTORE_R10));
else
BuildMI(allocMBB, DL, TII.get(X86::MORESTACK_RET));
allocMBB->addSuccessor(&PrologueMBB);
checkMBB->addSuccessor(allocMBB);
checkMBB->addSuccessor(&PrologueMBB);
#ifdef EXPENSIVE_CHECKS
MF.verify();
#endif
}
/// Lookup an ERTS parameter in the !hipe.literals named metadata node.
/// HiPE provides Erlang Runtime System-internal parameters, such as PCB offsets
/// to fields it needs, through a named metadata node "hipe.literals" containing
/// name-value pairs.
static unsigned getHiPELiteral(
NamedMDNode *HiPELiteralsMD, const StringRef LiteralName) {
for (int i = 0, e = HiPELiteralsMD->getNumOperands(); i != e; ++i) {
MDNode *Node = HiPELiteralsMD->getOperand(i);
if (Node->getNumOperands() != 2) continue;
MDString *NodeName = dyn_cast<MDString>(Node->getOperand(0));
ValueAsMetadata *NodeVal = dyn_cast<ValueAsMetadata>(Node->getOperand(1));
if (!NodeName || !NodeVal) continue;
ConstantInt *ValConst = dyn_cast_or_null<ConstantInt>(NodeVal->getValue());
if (ValConst && NodeName->getString() == LiteralName) {
return ValConst->getZExtValue();
}
}
report_fatal_error("HiPE literal " + LiteralName
+ " required but not provided");
}
/// Erlang programs may need a special prologue to handle the stack size they
/// might need at runtime. That is because Erlang/OTP does not implement a C
/// stack but uses a custom implementation of hybrid stack/heap architecture.
/// (for more information see Eric Stenman's Ph.D. thesis:
/// http://publications.uu.se/uu/fulltext/nbn_se_uu_diva-2688.pdf)
///
/// CheckStack:
/// temp0 = sp - MaxStack
/// if( temp0 < SP_LIMIT(P) ) goto IncStack else goto OldStart
/// OldStart:
/// ...
/// IncStack:
/// call inc_stack # doubles the stack space
/// temp0 = sp - MaxStack
/// if( temp0 < SP_LIMIT(P) ) goto IncStack else goto OldStart
void X86FrameLowering::adjustForHiPEPrologue(
MachineFunction &MF, MachineBasicBlock &PrologueMBB) const {
MachineFrameInfo &MFI = MF.getFrameInfo();
DebugLoc DL;
// To support shrink-wrapping we would need to insert the new blocks
// at the right place and update the branches to PrologueMBB.
assert(&(*MF.begin()) == &PrologueMBB && "Shrink-wrapping not supported yet");
// HiPE-specific values
NamedMDNode *HiPELiteralsMD = MF.getMMI().getModule()
->getNamedMetadata("hipe.literals");
if (!HiPELiteralsMD)
report_fatal_error(
"Can't generate HiPE prologue without runtime parameters");
const unsigned HipeLeafWords
= getHiPELiteral(HiPELiteralsMD,
Is64Bit ? "AMD64_LEAF_WORDS" : "X86_LEAF_WORDS");
const unsigned CCRegisteredArgs = Is64Bit ? 6 : 5;
const unsigned Guaranteed = HipeLeafWords * SlotSize;
unsigned CallerStkArity = MF.getFunction().arg_size() > CCRegisteredArgs ?
MF.getFunction().arg_size() - CCRegisteredArgs : 0;
unsigned MaxStack = MFI.getStackSize() + CallerStkArity*SlotSize + SlotSize;
assert(STI.isTargetLinux() &&
"HiPE prologue is only supported on Linux operating systems.");
// Compute the largest caller's frame that is needed to fit the callees'
// frames. This 'MaxStack' is computed from:
//
// a) the fixed frame size, which is the space needed for all spilled temps,
// b) outgoing on-stack parameter areas, and
// c) the minimum stack space this function needs to make available for the
// functions it calls (a tunable ABI property).
if (MFI.hasCalls()) {
unsigned MoreStackForCalls = 0;
for (auto &MBB : MF) {
for (auto &MI : MBB) {
if (!MI.isCall())
continue;
// Get callee operand.
const MachineOperand &MO = MI.getOperand(0);
// Only take account of global function calls (no closures etc.).
if (!MO.isGlobal())
continue;
const Function *F = dyn_cast<Function>(MO.getGlobal());
if (!F)
continue;
// Do not update 'MaxStack' for primitive and built-in functions
// (encoded with names either starting with "erlang."/"bif_" or not
// having a ".", such as a simple <Module>.<Function>.<Arity>, or an
// "_", such as the BIF "suspend_0") as they are executed on another
// stack.
if (F->getName().find("erlang.") != StringRef::npos ||
F->getName().find("bif_") != StringRef::npos ||
F->getName().find_first_of("._") == StringRef::npos)
continue;
unsigned CalleeStkArity =
F->arg_size() > CCRegisteredArgs ? F->arg_size()-CCRegisteredArgs : 0;
if (HipeLeafWords - 1 > CalleeStkArity)
MoreStackForCalls = std::max(MoreStackForCalls,
(HipeLeafWords - 1 - CalleeStkArity) * SlotSize);
}
}
MaxStack += MoreStackForCalls;
}
// If the stack frame needed is larger than the guaranteed then runtime checks
// and calls to "inc_stack_0" BIF should be inserted in the assembly prologue.
if (MaxStack > Guaranteed) {
MachineBasicBlock *stackCheckMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *incStackMBB = MF.CreateMachineBasicBlock();
for (const auto &LI : PrologueMBB.liveins()) {
stackCheckMBB->addLiveIn(LI);
incStackMBB->addLiveIn(LI);
}
MF.push_front(incStackMBB);
MF.push_front(stackCheckMBB);
unsigned ScratchReg, SPReg, PReg, SPLimitOffset;
unsigned LEAop, CMPop, CALLop;
SPLimitOffset = getHiPELiteral(HiPELiteralsMD, "P_NSP_LIMIT");
if (Is64Bit) {
SPReg = X86::RSP;
PReg = X86::RBP;
LEAop = X86::LEA64r;
CMPop = X86::CMP64rm;
CALLop = X86::CALL64pcrel32;
} else {
SPReg = X86::ESP;
PReg = X86::EBP;
LEAop = X86::LEA32r;
CMPop = X86::CMP32rm;
CALLop = X86::CALLpcrel32;
}
ScratchReg = GetScratchRegister(Is64Bit, IsLP64, MF, true);
assert(!MF.getRegInfo().isLiveIn(ScratchReg) &&
"HiPE prologue scratch register is live-in");
// Create new MBB for StackCheck:
addRegOffset(BuildMI(stackCheckMBB, DL, TII.get(LEAop), ScratchReg),
SPReg, false, -MaxStack);
// SPLimitOffset is in a fixed heap location (pointed by BP).
addRegOffset(BuildMI(stackCheckMBB, DL, TII.get(CMPop))
.addReg(ScratchReg), PReg, false, SPLimitOffset);
BuildMI(stackCheckMBB, DL, TII.get(X86::JAE_1)).addMBB(&PrologueMBB);
// Create new MBB for IncStack:
BuildMI(incStackMBB, DL, TII.get(CALLop)).
addExternalSymbol("inc_stack_0");
addRegOffset(BuildMI(incStackMBB, DL, TII.get(LEAop), ScratchReg),
SPReg, false, -MaxStack);
addRegOffset(BuildMI(incStackMBB, DL, TII.get(CMPop))
.addReg(ScratchReg), PReg, false, SPLimitOffset);
BuildMI(incStackMBB, DL, TII.get(X86::JLE_1)).addMBB(incStackMBB);
stackCheckMBB->addSuccessor(&PrologueMBB, {99, 100});
stackCheckMBB->addSuccessor(incStackMBB, {1, 100});
incStackMBB->addSuccessor(&PrologueMBB, {99, 100});
incStackMBB->addSuccessor(incStackMBB, {1, 100});
}
#ifdef EXPENSIVE_CHECKS
MF.verify();
#endif
}
bool X86FrameLowering::adjustStackWithPops(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL,
int Offset) const {
if (Offset <= 0)
return false;
if (Offset % SlotSize)
return false;
int NumPops = Offset / SlotSize;
// This is only worth it if we have at most 2 pops.
if (NumPops != 1 && NumPops != 2)
return false;
// Handle only the trivial case where the adjustment directly follows
// a call. This is the most common one, anyway.
if (MBBI == MBB.begin())
return false;
MachineBasicBlock::iterator Prev = std::prev(MBBI);
if (!Prev->isCall() || !Prev->getOperand(1).isRegMask())
return false;
unsigned Regs[2];
unsigned FoundRegs = 0;
auto &MRI = MBB.getParent()->getRegInfo();
auto RegMask = Prev->getOperand(1);
auto &RegClass =
Is64Bit ? X86::GR64_NOREX_NOSPRegClass : X86::GR32_NOREX_NOSPRegClass;
// Try to find up to NumPops free registers.
for (auto Candidate : RegClass) {
// Poor man's liveness:
// Since we're immediately after a call, any register that is clobbered
// by the call and not defined by it can be considered dead.
if (!RegMask.clobbersPhysReg(Candidate))
continue;
// Don't clobber reserved registers
if (MRI.isReserved(Candidate))
continue;
bool IsDef = false;
for (const MachineOperand &MO : Prev->implicit_operands()) {
if (MO.isReg() && MO.isDef() &&
TRI->isSuperOrSubRegisterEq(MO.getReg(), Candidate)) {
IsDef = true;
break;
}
}
if (IsDef)
continue;
Regs[FoundRegs++] = Candidate;
if (FoundRegs == (unsigned)NumPops)
break;
}
if (FoundRegs == 0)
return false;
// If we found only one free register, but need two, reuse the same one twice.
while (FoundRegs < (unsigned)NumPops)
Regs[FoundRegs++] = Regs[0];
for (int i = 0; i < NumPops; ++i)
BuildMI(MBB, MBBI, DL,
TII.get(STI.is64Bit() ? X86::POP64r : X86::POP32r), Regs[i]);
return true;
}
MachineBasicBlock::iterator X86FrameLowering::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
bool reserveCallFrame = hasReservedCallFrame(MF);
unsigned Opcode = I->getOpcode();
bool isDestroy = Opcode == TII.getCallFrameDestroyOpcode();
DebugLoc DL = I->getDebugLoc();
uint64_t Amount = !reserveCallFrame ? TII.getFrameSize(*I) : 0;
uint64_t InternalAmt = (isDestroy || Amount) ? TII.getFrameAdjustment(*I) : 0;
I = MBB.erase(I);
auto InsertPos = skipDebugInstructionsForward(I, MBB.end());
if (!reserveCallFrame) {
// If the stack pointer can be changed after prologue, turn the
// adjcallstackup instruction into a 'sub ESP, <amt>' and the
// adjcallstackdown instruction into 'add ESP, <amt>'
// We need to keep the stack aligned properly. To do this, we round the
// amount of space needed for the outgoing arguments up to the next
// alignment boundary.
unsigned StackAlign = getStackAlignment();
Amount = alignTo(Amount, StackAlign);
MachineModuleInfo &MMI = MF.getMMI();
const Function &F = MF.getFunction();
bool WindowsCFI = MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
bool DwarfCFI = !WindowsCFI &&
(MMI.hasDebugInfo() || F.needsUnwindTableEntry());
// If we have any exception handlers in this function, and we adjust
// the SP before calls, we may need to indicate this to the unwinder
// using GNU_ARGS_SIZE. Note that this may be necessary even when
// Amount == 0, because the preceding function may have set a non-0
// GNU_ARGS_SIZE.
// TODO: We don't need to reset this between subsequent functions,
// if it didn't change.
bool HasDwarfEHHandlers = !WindowsCFI && !MF.getLandingPads().empty();
if (HasDwarfEHHandlers && !isDestroy &&
MF.getInfo<X86MachineFunctionInfo>()->getHasPushSequences())
BuildCFI(MBB, InsertPos, DL,
MCCFIInstruction::createGnuArgsSize(nullptr, Amount));
if (Amount == 0)
return I;
// Factor out the amount that gets handled inside the sequence
// (Pushes of argument for frame setup, callee pops for frame destroy)
Amount -= InternalAmt;
// TODO: This is needed only if we require precise CFA.
// If this is a callee-pop calling convention, emit a CFA adjust for
// the amount the callee popped.
if (isDestroy && InternalAmt && DwarfCFI && !hasFP(MF))
BuildCFI(MBB, InsertPos, DL,
MCCFIInstruction::createAdjustCfaOffset(nullptr, -InternalAmt));
// Add Amount to SP to destroy a frame, or subtract to setup.
int64_t StackAdjustment = isDestroy ? Amount : -Amount;
int64_t CfaAdjustment = -StackAdjustment;
if (StackAdjustment) {
// Merge with any previous or following adjustment instruction. Note: the
// instructions merged with here do not have CFI, so their stack
// adjustments do not feed into CfaAdjustment.
StackAdjustment += mergeSPUpdates(MBB, InsertPos, true);
StackAdjustment += mergeSPUpdates(MBB, InsertPos, false);
if (StackAdjustment) {
if (!(F.optForMinSize() &&
adjustStackWithPops(MBB, InsertPos, DL, StackAdjustment)))
BuildStackAdjustment(MBB, InsertPos, DL, StackAdjustment,
/*InEpilogue=*/false);
}
}
if (DwarfCFI && !hasFP(MF)) {
// If we don't have FP, but need to generate unwind information,
// we need to set the correct CFA offset after the stack adjustment.
// How much we adjust the CFA offset depends on whether we're emitting
// CFI only for EH purposes or for debugging. EH only requires the CFA
// offset to be correct at each call site, while for debugging we want
// it to be more precise.
// TODO: When not using precise CFA, we also need to adjust for the
// InternalAmt here.
if (CfaAdjustment) {
BuildCFI(MBB, InsertPos, DL,
MCCFIInstruction::createAdjustCfaOffset(nullptr,
CfaAdjustment));
}
}
return I;
}
if (isDestroy && InternalAmt) {
// If we are performing frame pointer elimination and if the callee pops
// something off the stack pointer, add it back. We do this until we have
// more advanced stack pointer tracking ability.
// We are not tracking the stack pointer adjustment by the callee, so make
// sure we restore the stack pointer immediately after the call, there may
// be spill code inserted between the CALL and ADJCALLSTACKUP instructions.
MachineBasicBlock::iterator CI = I;
MachineBasicBlock::iterator B = MBB.begin();
while (CI != B && !std::prev(CI)->isCall())
--CI;
BuildStackAdjustment(MBB, CI, DL, -InternalAmt, /*InEpilogue=*/false);
}
return I;
}
bool X86FrameLowering::canUseAsPrologue(const MachineBasicBlock &MBB) const {
assert(MBB.getParent() && "Block is not attached to a function!");
const MachineFunction &MF = *MBB.getParent();
return !TRI->needsStackRealignment(MF) || !MBB.isLiveIn(X86::EFLAGS);
}
bool X86FrameLowering::canUseAsEpilogue(const MachineBasicBlock &MBB) const {
assert(MBB.getParent() && "Block is not attached to a function!");
// Win64 has strict requirements in terms of epilogue and we are
// not taking a chance at messing with them.
// I.e., unless this block is already an exit block, we can't use
// it as an epilogue.
if (STI.isTargetWin64() && !MBB.succ_empty() && !MBB.isReturnBlock())
return false;
if (canUseLEAForSPInEpilogue(*MBB.getParent()))
return true;
// If we cannot use LEA to adjust SP, we may need to use ADD, which
// clobbers the EFLAGS. Check that we do not need to preserve it,
// otherwise, conservatively assume this is not
// safe to insert the epilogue here.
return !flagsNeedToBePreservedBeforeTheTerminators(MBB);
}
bool X86FrameLowering::enableShrinkWrapping(const MachineFunction &MF) const {
// If we may need to emit frameless compact unwind information, give
// up as this is currently broken: PR25614.
return (MF.getFunction().hasFnAttribute(Attribute::NoUnwind) || hasFP(MF)) &&
// The lowering of segmented stack and HiPE only support entry blocks
// as prologue blocks: PR26107.
// This limitation may be lifted if we fix:
// - adjustForSegmentedStacks
// - adjustForHiPEPrologue
MF.getFunction().getCallingConv() != CallingConv::HiPE &&
!MF.shouldSplitStack();
}
MachineBasicBlock::iterator X86FrameLowering::restoreWin32EHStackPointers(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
const DebugLoc &DL, bool RestoreSP) const {
assert(STI.isTargetWindowsMSVC() && "funclets only supported in MSVC env");
assert(STI.isTargetWin32() && "EBP/ESI restoration only required on win32");
assert(STI.is32Bit() && !Uses64BitFramePtr &&
"restoring EBP/ESI on non-32-bit target");
MachineFunction &MF = *MBB.getParent();
unsigned FramePtr = TRI->getFrameRegister(MF);
unsigned BasePtr = TRI->getBaseRegister();
WinEHFuncInfo &FuncInfo = *MF.getWinEHFuncInfo();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
MachineFrameInfo &MFI = MF.getFrameInfo();
// FIXME: Don't set FrameSetup flag in catchret case.
int FI = FuncInfo.EHRegNodeFrameIndex;
int EHRegSize = MFI.getObjectSize(FI);
if (RestoreSP) {
// MOV32rm -EHRegSize(%ebp), %esp
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32rm), X86::ESP),
X86::EBP, true, -EHRegSize)
.setMIFlag(MachineInstr::FrameSetup);
}
unsigned UsedReg;
int EHRegOffset = getFrameIndexReference(MF, FI, UsedReg);
int EndOffset = -EHRegOffset - EHRegSize;
FuncInfo.EHRegNodeEndOffset = EndOffset;
if (UsedReg == FramePtr) {
// ADD $offset, %ebp
unsigned ADDri = getADDriOpcode(false, EndOffset);
BuildMI(MBB, MBBI, DL, TII.get(ADDri), FramePtr)
.addReg(FramePtr)
.addImm(EndOffset)
.setMIFlag(MachineInstr::FrameSetup)
->getOperand(3)
.setIsDead();
assert(EndOffset >= 0 &&
"end of registration object above normal EBP position!");
} else if (UsedReg == BasePtr) {
// LEA offset(%ebp), %esi
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::LEA32r), BasePtr),
FramePtr, false, EndOffset)
.setMIFlag(MachineInstr::FrameSetup);
// MOV32rm SavedEBPOffset(%esi), %ebp
assert(X86FI->getHasSEHFramePtrSave());
int Offset =
getFrameIndexReference(MF, X86FI->getSEHFramePtrSaveIndex(), UsedReg);
assert(UsedReg == BasePtr);
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32rm), FramePtr),
UsedReg, true, Offset)
.setMIFlag(MachineInstr::FrameSetup);
} else {
llvm_unreachable("32-bit frames with WinEH must use FramePtr or BasePtr");
}
return MBBI;
}
namespace {
// Struct used by orderFrameObjects to help sort the stack objects.
struct X86FrameSortingObject {
bool IsValid = false; // true if we care about this Object.
unsigned ObjectIndex = 0; // Index of Object into MFI list.
unsigned ObjectSize = 0; // Size of Object in bytes.
unsigned ObjectAlignment = 1; // Alignment of Object in bytes.
unsigned ObjectNumUses = 0; // Object static number of uses.
};
// The comparison function we use for std::sort to order our local
// stack symbols. The current algorithm is to use an estimated
// "density". This takes into consideration the size and number of
// uses each object has in order to roughly minimize code size.
// So, for example, an object of size 16B that is referenced 5 times
// will get higher priority than 4 4B objects referenced 1 time each.
// It's not perfect and we may be able to squeeze a few more bytes out of
// it (for example : 0(esp) requires fewer bytes, symbols allocated at the
// fringe end can have special consideration, given their size is less
// important, etc.), but the algorithmic complexity grows too much to be
// worth the extra gains we get. This gets us pretty close.
// The final order leaves us with objects with highest priority going
// at the end of our list.
struct X86FrameSortingComparator {
inline bool operator()(const X86FrameSortingObject &A,
const X86FrameSortingObject &B) {
uint64_t DensityAScaled, DensityBScaled;
// For consistency in our comparison, all invalid objects are placed
// at the end. This also allows us to stop walking when we hit the
// first invalid item after it's all sorted.
if (!A.IsValid)
return false;
if (!B.IsValid)
return true;
// The density is calculated by doing :
// (double)DensityA = A.ObjectNumUses / A.ObjectSize
// (double)DensityB = B.ObjectNumUses / B.ObjectSize
// Since this approach may cause inconsistencies in
// the floating point <, >, == comparisons, depending on the floating
// point model with which the compiler was built, we're going
// to scale both sides by multiplying with
// A.ObjectSize * B.ObjectSize. This ends up factoring away
// the division and, with it, the need for any floating point
// arithmetic.
DensityAScaled = static_cast<uint64_t>(A.ObjectNumUses) *
static_cast<uint64_t>(B.ObjectSize);
DensityBScaled = static_cast<uint64_t>(B.ObjectNumUses) *
static_cast<uint64_t>(A.ObjectSize);
// If the two densities are equal, prioritize highest alignment
// objects. This allows for similar alignment objects
// to be packed together (given the same density).
// There's room for improvement here, also, since we can pack
// similar alignment (different density) objects next to each
// other to save padding. This will also require further
// complexity/iterations, and the overall gain isn't worth it,
// in general. Something to keep in mind, though.
if (DensityAScaled == DensityBScaled)
return A.ObjectAlignment < B.ObjectAlignment;
return DensityAScaled < DensityBScaled;
}
};
} // namespace
// Order the symbols in the local stack.
// We want to place the local stack objects in some sort of sensible order.
// The heuristic we use is to try and pack them according to static number
// of uses and size of object in order to minimize code size.
void X86FrameLowering::orderFrameObjects(
const MachineFunction &MF, SmallVectorImpl<int> &ObjectsToAllocate) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
// Don't waste time if there's nothing to do.
if (ObjectsToAllocate.empty())
return;
// Create an array of all MFI objects. We won't need all of these
// objects, but we're going to create a full array of them to make
// it easier to index into when we're counting "uses" down below.
// We want to be able to easily/cheaply access an object by simply
// indexing into it, instead of having to search for it every time.
std::vector<X86FrameSortingObject> SortingObjects(MFI.getObjectIndexEnd());
// Walk the objects we care about and mark them as such in our working
// struct.
for (auto &Obj : ObjectsToAllocate) {
SortingObjects[Obj].IsValid = true;
SortingObjects[Obj].ObjectIndex = Obj;
SortingObjects[Obj].ObjectAlignment = MFI.getObjectAlignment(Obj);
// Set the size.
int ObjectSize = MFI.getObjectSize(Obj);
if (ObjectSize == 0)
// Variable size. Just use 4.
SortingObjects[Obj].ObjectSize = 4;
else
SortingObjects[Obj].ObjectSize = ObjectSize;
}
// Count the number of uses for each object.
for (auto &MBB : MF) {
for (auto &MI : MBB) {
if (MI.isDebugValue())
continue;
for (const MachineOperand &MO : MI.operands()) {
// Check to see if it's a local stack symbol.
if (!MO.isFI())
continue;
int Index = MO.getIndex();
// Check to see if it falls within our range, and is tagged
// to require ordering.
if (Index >= 0 && Index < MFI.getObjectIndexEnd() &&
SortingObjects[Index].IsValid)
SortingObjects[Index].ObjectNumUses++;
}
}
}
// Sort the objects using X86FrameSortingAlgorithm (see its comment for
// info).
std::stable_sort(SortingObjects.begin(), SortingObjects.end(),
X86FrameSortingComparator());
// Now modify the original list to represent the final order that
// we want. The order will depend on whether we're going to access them
// from the stack pointer or the frame pointer. For SP, the list should
// end up with the END containing objects that we want with smaller offsets.
// For FP, it should be flipped.
int i = 0;
for (auto &Obj : SortingObjects) {
// All invalid items are sorted at the end, so it's safe to stop.
if (!Obj.IsValid)
break;
ObjectsToAllocate[i++] = Obj.ObjectIndex;
}
// Flip it if we're accessing off of the FP.
if (!TRI->needsStackRealignment(MF) && hasFP(MF))
std::reverse(ObjectsToAllocate.begin(), ObjectsToAllocate.end());
}
unsigned X86FrameLowering::getWinEHParentFrameOffset(const MachineFunction &MF) const {
// RDX, the parent frame pointer, is homed into 16(%rsp) in the prologue.
unsigned Offset = 16;
// RBP is immediately pushed.
Offset += SlotSize;
// All callee-saved registers are then pushed.
Offset += MF.getInfo<X86MachineFunctionInfo>()->getCalleeSavedFrameSize();
// Every funclet allocates enough stack space for the largest outgoing call.
Offset += getWinEHFuncletFrameSize(MF);
return Offset;
}
void X86FrameLowering::processFunctionBeforeFrameFinalized(
MachineFunction &MF, RegScavenger *RS) const {
// Mark the function as not having WinCFI. We will set it back to true in
// emitPrologue if it gets called and emits CFI.
MF.setHasWinCFI(false);
// If this function isn't doing Win64-style C++ EH, we don't need to do
// anything.
const Function &F = MF.getFunction();
if (!STI.is64Bit() || !MF.hasEHFunclets() ||
classifyEHPersonality(F.getPersonalityFn()) != EHPersonality::MSVC_CXX)
return;
// Win64 C++ EH needs to allocate the UnwindHelp object at some fixed offset
// relative to RSP after the prologue. Find the offset of the last fixed
// object, so that we can allocate a slot immediately following it. If there
// were no fixed objects, use offset -SlotSize, which is immediately after the
// return address. Fixed objects have negative frame indices.
MachineFrameInfo &MFI = MF.getFrameInfo();
WinEHFuncInfo &EHInfo = *MF.getWinEHFuncInfo();
int64_t MinFixedObjOffset = -SlotSize;
for (int I = MFI.getObjectIndexBegin(); I < 0; ++I)
MinFixedObjOffset = std::min(MinFixedObjOffset, MFI.getObjectOffset(I));
for (WinEHTryBlockMapEntry &TBME : EHInfo.TryBlockMap) {
for (WinEHHandlerType &H : TBME.HandlerArray) {
int FrameIndex = H.CatchObj.FrameIndex;
if (FrameIndex != INT_MAX) {
// Ensure alignment.
unsigned Align = MFI.getObjectAlignment(FrameIndex);
MinFixedObjOffset -= std::abs(MinFixedObjOffset) % Align;
MinFixedObjOffset -= MFI.getObjectSize(FrameIndex);
MFI.setObjectOffset(FrameIndex, MinFixedObjOffset);
}
}
}
// Ensure alignment.
MinFixedObjOffset -= std::abs(MinFixedObjOffset) % 8;
int64_t UnwindHelpOffset = MinFixedObjOffset - SlotSize;
int UnwindHelpFI =
MFI.CreateFixedObject(SlotSize, UnwindHelpOffset, /*Immutable=*/false);
EHInfo.UnwindHelpFrameIdx = UnwindHelpFI;
// Store -2 into UnwindHelp on function entry. We have to scan forwards past
// other frame setup instructions.
MachineBasicBlock &MBB = MF.front();
auto MBBI = MBB.begin();
while (MBBI != MBB.end() && MBBI->getFlag(MachineInstr::FrameSetup))
++MBBI;
DebugLoc DL = MBB.findDebugLoc(MBBI);
addFrameReference(BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64mi32)),
UnwindHelpFI)
.addImm(-2);
}
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